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Investment Income And Gains And Losses (Net Unrealized Gains (Losses), Including Portion Of Other-Than-Temporary Impairments Included In Accumulated Other Comprehensive Income (Loss), Reported Within Shareholders' Equity) (Details) (USD $) In Millions, unless otherwise specified | Mar. 31, 2012 | Dec. 31, 2011
--- | --- | ---
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items] |  |
Deferred income tax provision (benefit) | $ (20) | $ (86)
Unrealized gains (losses), net | 17 | (134)
Total | (3) | (220)
Fixed-Maturity Investments [Member] |  |
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items] |  |
Gains | 252 | 262
Losses | (278) | (459)
Foreign exchange | 21 | (5)
Net | (5) | (202)
Other Investments [Member] |  |
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items] |  |
Gains | 2 | 1
Losses |  | (19)
Net | $ 2 | $ (18)

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