|**Benefit Plans (Fair Value of Plan Assets Measured on a Recurring Basis) (Details) - USD ($) $ in Millions**                                                                                                                                                                                                                                                                                                       | Dec. 31, 2016                                                                                                                                                                                                                                                                                                                                                                                                   | Dec. 31, 2015                                                                                                                                                                                                                                                                                                                                                                                                   | Dec. 31, 2014
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Defined Benefit Plan, Assets for Plan Benefits                                                                                                                                                                                                                                                                                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                 | $ 2,193                                                                                                                                                                                                                                                                                                                                                                                                         | $ 2,267      
|Corporate and other bonds [Member]                                                                                                                                                                                                                                                                                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 510                                                                                                                                                                                                                                                                                                                                                                                                             | 465          
|Corporate and other bonds [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Corporate and other bonds [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 500                                                                                                                                                                                                                                                                                                                                                                                                             | 455          
|Corporate and other bonds [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 10                                                                                                                                                                                                                                                                                                                                                                                                              | 10           
|States, municipalities and political subdivisions [Member]                                                                                                                                                                                                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 63                                                                                                                                                                                                                                                                                                                                                                                                              | 106          
|States, municipalities and political subdivisions [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|States, municipalities and political subdivisions [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 63                                                                                                                                                                                                                                                                                                                                                                                                              | 106          
|States, municipalities and political subdivisions [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Residential mortgage-backed [Member]                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 109                                                                                                                                                                                                                                                                                                                                                                                                             | 133          
|Residential mortgage-backed [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Residential mortgage-backed [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 109                                                                                                                                                                                                                                                                                                                                                                                                             | 133          
|Residential mortgage-backed [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Commercial Mortgage Backed Securities [Member]                                                                                                                                                                                                                                                                                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 66                                                                                                                                                                                                                                                                                                                                                                                                              | 69           
|Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 66                                                                                                                                                                                                                                                                                                                                                                                                              | 69           
|Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Other asset-backed [Member]                                                                                                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 4                                                                                                                                                                                                                                                                                                                                                                                                               | 11           
|Other asset-backed [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Other asset-backed [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 4                                                                                                                                                                                                                                                                                                                                                                                                               | 11           
|Other asset-backed [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Total asset-backed [Member]                                                                                                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 179                                                                                                                                                                                                                                                                                                                                                                                                             | 213          
|Total asset-backed [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Total asset-backed [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 179                                                                                                                                                                                                                                                                                                                                                                                                             | 213          
|Total asset-backed [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Fixed Maturities [Member]                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 752                                                                                                                                                                                                                                                                                                                                                                                                             | 784          
|Fixed Maturities [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Fixed Maturities [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 742                                                                                                                                                                                                                                                                                                                                                                                                             | 774          
|Fixed Maturities [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 10                                                                                                                                                                                                                                                                                                                                                                                                              | 10           
|Equity securities [Member]                                                                                                                                                                                                                                                                                                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 468                                                                                                                                                                                                                                                                                                                                                                                                             | 443          
|Equity securities [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 363                                                                                                                                                                                                                                                                                                                                                                                                             | 336          
|Equity securities [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 105                                                                                                                                                                                                                                                                                                                                                                                                             | 107          
|Equity securities [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Derivative Financial Instruments, Assets [Member]                                                                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 1            
|Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 1            
|Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Derivative Financial Instruments, Assets [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Short-term Investments [Member]                                                                                                                                                                                                                                                                                                                                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 46                                                                                                                                                                                                                                                                                                                                                                                                              | 52           
|Short-term Investments [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 11                                                                                                                                                                                                                                                                                                                                                                                                              | 24           
|Short-term Investments [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 35                                                                                                                                                                                                                                                                                                                                                                                                              | 28           
|Short-term Investments [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Other assets [Member]                                                                                                                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 37                                                                                                                                                                                                                                                                                                                                                                                                              | 52           
|Other assets [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Other assets [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 37                                                                                                                                                                                                                                                                                                                                                                                                              | 52           
|Other assets [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               | 0            
|Cash [Member]                                                                                                                                                                                                                                                                                                                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 14                                                                                                                                                                                                                                                                                                                                                                                                              |              
|Cash [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 14                                                                                                                                                                                                                                                                                                                                                                                                              |              
|Cash [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               |              
|Cash [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 0                                                                                                                                                                                                                                                                                                                                                                                                               |              
|Total assets [Member]                                                                                                                                                                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 1,317                                                                                                                                                                                                                                                                                                                                                                                                           | 1,332        
|Total assets [Member] | Fair Value, Inputs, Level 1 [Member]                                                                                                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 388                                                                                                                                                                                                                                                                                                                                                                                                             | 361          
|Total assets [Member] | Fair Value, Inputs, Level 2 [Member]                                                                                                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 919                                                                                                                                                                                                                                                                                                                                                                                                             | 961          
|Total assets [Member] | Fair Value, Inputs, Level 3 [Member]                                                                                                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Fair value of plan assets                                                                                                                                                                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                 | 10                                                                                                                                                                                                                                                                                                                                                                                                              | 10           
|Total limited partnerships [Member]                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|**Defined Benefit Plan Disclosure [Line Items]**                                                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                 |              
|Defined Benefit Plan, Assets for Plan Benefits                                                                                                                                                                                                                                                                                                                                                                      | [1]                                                                                                                                                                                                                                                                                                                                                                                                             | $ 876                                                                                                                                                                                                                                                                                                                                                                                                           | $ 935        
|                                                                                                                                                                                                                                                                                                                                                                                                                   
|[1]
(1) In accordance with Subtopic 820-10, certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statement of financial position. | [1]                                                                                                                                                                                                                                                                                                                                                                                                             | (1) In accordance with Subtopic 820-10, certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statement of financial position.
|[1]                                                                                                                                                                                                                                                                                                                                                                                                                 | (1) In accordance with Subtopic 820-10, certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statement of financial position.

X- DefinitionThis represents the entire assets recognized in the balance sheet that are associated with the defined benefit plans.
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