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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) (Detail) (USD $) In Millions, unless otherwise specified | Sep. 30, 2012 | Dec. 31, 2011
--- | --- | ---
Schedule of Investments [Line Items] |  |
Total | $ 163 | $ (220)
Deferred income tax provision (benefit) | 35 | (86)
Unrealized gains (losses), net | 128 | (134)
Fixed-Maturity Investments [Member] |  |
Schedule of Investments [Line Items] |  |
Gains | 337 | 262
Losses | (191) | (459)
Foreign exchange | 17 | (5)
Net | 163 | (202)
Other Investments [Member] |  |
Schedule of Investments [Line Items] |  |
Gains |  | 1
Losses |  | (19)
Net |  | $ (18)

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