|**Investments (Net realized investment gains (losses)) (Details) (USD $)In Millions, unless otherwise specified**                                                                                                                                                            | 12 Months Ended                                                                                                                                                                                                                                           
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|
|**Gain (Loss) on Investments**                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                           
|Net realized investment gains (losses), net of participating policyholders’ interests                                                                                                                                                                                        | $ (4)                                                                                                                                                                                                                                                     
|Fixed maturity securities [Member]                                                                                                                                                                                                                                           |                                                                                                                                                                                                                                                           
|**Gain (Loss) on Investments**                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                           
|Gross realized gains                                                                                                                                                                                                                                                         | 289                                                                                                                                                                                                                                                       
|Gross realized losses                                                                                                                                                                                                                                                        | (311)                                                                                                                                                                                                                                                     
|Net realized investment gains (losses), net of participating policyholders’ interests                                                                                                                                                                                        | (22)                                                                                                                                                                                                                                                      
|Equity securities [Member]                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                           
|**Gain (Loss) on Investments**                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                           
|Gross realized gains                                                                                                                                                                                                                                                         | 10                                                                                                                                                                                                                                                        
|Gross realized losses                                                                                                                                                                                                                                                        | (11)                                                                                                                                                                                                                                                      
|Net realized investment gains (losses), net of participating policyholders’ interests                                                                                                                                                                                        | (1)                                                                                                                                                                                                                                                       
|Derivatives [Member]                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                           
|**Gain (Loss) on Investments**                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                           
|Net realized investment gains (losses), net of participating policyholders’ interests                                                                                                                                                                                        |                                                                                                                                                                                                                                                           
|Short term investments and other [Member]                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                           
|**Gain (Loss) on Investments**                                                                                                                                                                                                                                               |                                                                                                                                                                                                                                                           
|Net realized investment gains (losses), net of participating policyholders’ interests                                                                                                                                                                                        | $ 19                                                                                                                                                                                                                                                      
|                                                                                                                                                                                                                                                                            
|[1]
              Includes net unrealized gains (losses) related to changes in the fair value of securities for which the fair value option has been elected. Net unrealized gains (losses) were $2 million and $(1) million for the years ended December 31, 2011 and 2010. | [1]                                                                                                                                                                                                                                                       
|[1]                                                                                                                                                                                                                                                                          | Includes net unrealized gains (losses) related to changes in the fair value of securities for which the fair value option has been elected. Net unrealized gains (losses) were $2 million and $(1) million for the years ended December 31, 2011 and 2010.

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