Investment Income And Gains And Losses (Net Unrealized Gains (Losses), Including Portion Of Other-Than-Temporary Impairments Included In Other Comprehensive Loss, Reported Within Shareholders' Equity) (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Deferred income tax provision (benefit)	$ (76)	$ (208)
Unrealized gains (losses), net	(107)	(392)
Total	(183)	(600)
Fixed-Maturity Investments [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Gains	373	208
Losses	(536)	(782)
Foreign exchange	9	(14)
Net	(154)	(588)
Other Investments [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Gains	2	10
Losses	(31)	(22)
Net	$ (29)	$ (12)