| **Fair Value Measurements (Fair Value of Life Policy) (Details) - USD ($) $ in Millions** | Dec. 31, 2018 | Dec. 31, 2017 |
|-------------------------------------------------------------------------------------------|---------------|---------------|
| **Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis**        |          |          |
| Fair value of life policy loans                                                           | $ 40          | $ 41          |
| Level 1                                                                                   |          |          |
| **Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis**        |          |          |
| Fair value of life policy loans                                                           | 0             | 0             |
| Level 2                                                                                   |          |          |
| **Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis**        |          |          |
| Fair value of life policy loans                                                           | 0             | 0             |
| Level 3                                                                                   |          |          |
| **Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis**        |          |          |
| Fair value of life policy loans                                                           | $ 40          | $ 41          |

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| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
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| - Definition
Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -URI http://asc.fasb.org/subtopic&trid=2196772
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