Investments (Details 7) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Investments
Net unrealized gains related to changes in valuation of fixed income securities subsequent to impairment measurement date	$ 225		$ 225		$ 172
Other-than 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	(387)		(387)		(439)
Credit Losses on Fixed Income Securities
Balance	(820)	(963)	(944)	(1,046)
Additional credit loss for securities previously other-than-temporarily impaired	(16)	(31)	(36)	(90)
Additional credit loss for securities not previously other-than-temporarily impaired	(10)	(17)	(19)	(44)
Reduction in credit loss for securities disposed or collected	65	94	211	247
Reduction in credit loss for securities the Company has made the decision to sell or more likely than not will be required to sell			7	15
Change in credit loss due to accretion of increase in cash flows		5		6
Balance	(781)	(912)	(781)	(912)
Municipal
Other-than 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	(28)		(28)		(11)
Corporate
Other-than 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	(34)		(34)		(35)
Residential mortgage-backed securities ("RMBS")
Other-than 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	(283)		(283)		(353)
Commercial mortgage-backed securities ("CMBS")
Other-than 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	(22)		(22)		(19)
Asset-backed securities ("ABS")
Other-than 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	$ (20)		$ (20)		$ (21)