Investments (Details 7) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Investments
Net unrealized gains related to changes in valuation of fixed income securities subsequent to impairment measurement date	$ 137		$ 137		$ 90
Rollforwards of the cumulative credit losses recognized in earnings for fixed income securities
Beginning balance	(460)	(544)	(581)	(701)
Additional credit loss for securities previously other-than-temporarily impaired	(7)	(30)	(29)	(62)
Additional credit loss for securities not previously other-than-temporarily impaired	(2)	(21)	(10)	(61)
Reduction in credit loss for securities disposed or collected	80	45	231	255
Reduction in credit loss for securities the Company has made the decision to sell or more likely than not will be required to sell				13
Change in credit loss due to accretion of increase in cash flows		3		9
Ending balance	(389)	(547)	(389)	(547)
Municipal
Other-than-temporary impairment losses included in accumulated other comprehensive income
Amount of other-than-temporary impairment losses included in accumulated other comprehensive income for fixed income securities, not included in earnings	(5)		(5)		(5)
Corporate
Other-than-temporary impairment losses included in accumulated other comprehensive income
Amount of other-than-temporary impairment losses included in accumulated other comprehensive income for fixed income securities, not included in earnings	(1)		(1)		(6)
RMBS
Other-than-temporary impairment losses included in accumulated other comprehensive income
Amount of other-than-temporary impairment losses included in accumulated other comprehensive income for fixed income securities, not included in earnings	(134)		(134)		(198)
CMBS
Other-than-temporary impairment losses included in accumulated other comprehensive income
Amount of other-than-temporary impairment losses included in accumulated other comprehensive income for fixed income securities, not included in earnings	(21)		(21)		(19)
ABS
Other-than-temporary impairment losses included in accumulated other comprehensive income
Amount of other-than-temporary impairment losses included in accumulated other comprehensive income for fixed income securities, not included in earnings	(14)		(14)		(21)
Fixed income securities
Other-than-temporary impairment losses included in accumulated other comprehensive income
Amount of other-than-temporary impairment losses included in accumulated other comprehensive income for fixed income securities, not included in earnings	$ (175)		$ (175)		$ (249)