Investments (Details 7) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Investments
Net unrealized gains related to changes in valuation of fixed income securities subsequent to impairment measurement date	$ 161		$ 161		$ 134
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	(124)		(124)		(142)
Credit Losses on Fixed Income Securities
Beginning balance	(318)	(460)	(345)	(581)
Additional credit loss for securities previously other-than-temporarily impaired		(7)	(12)	(29)
Additional credit loss for securities not previously other-than-temporarily impaired	(2)	(2)	(19)	(10)
Reduction in credit loss for securities disposed or collected	12	80	68	231
Ending balance	(308)	(389)	(308)	(389)
Cumulative credit losses recognized in earnings for securities classified as held for sale	59		59
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	(7)		(7)		(1)
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	(10)		(10)		(14)
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	(86)		(86)		(103)
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	$ (16)		$ (16)		$ (19)