Investments (Details 6) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment losses	$ (87)	$ (156)
Portion of loss recognized in other comprehensive income	4	(27)
Net other-than-temporary impairment losses recognized in earnings	(83)	(183)
Fixed income securities
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment losses	(68)	(128)
Portion of loss recognized in other comprehensive income	4	(27)
Net other-than-temporary impairment losses recognized in earnings	(64)	(155)
Municipal
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment losses	(1)	(27)
Portion of loss recognized in other comprehensive income		(2)
Net other-than-temporary impairment losses recognized in earnings	(1)	(29)
Corporate
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment losses	(18)	(5)
Portion of loss recognized in other comprehensive income		1
Net other-than-temporary impairment losses recognized in earnings	(18)	(4)
Foreign government
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment losses		(1)
Net other-than-temporary impairment losses recognized in earnings		(1)
Residential mortgage-backed securities ("RMBS")
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment losses	(43)	(72)
Portion of loss recognized in other comprehensive income	4	(25)
Net other-than-temporary impairment losses recognized in earnings	(39)	(97)
Commercial mortgage-backed securities ("CMBS")
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment losses	(6)	(16)
Portion of loss recognized in other comprehensive income		(4)
Net other-than-temporary impairment losses recognized in earnings	(6)	(20)
Asset-backed securities ("ABS")
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment losses		(7)
Portion of loss recognized in other comprehensive income		3
Net other-than-temporary impairment losses recognized in earnings		(4)
Equity securities
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment losses	(16)	(20)
Net other-than-temporary impairment losses recognized in earnings	(16)	(20)
Mortgage loans
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment losses	(3)	(6)
Net other-than-temporary impairment losses recognized in earnings	(3)	(6)
Limited partnership interests
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment losses	(2)	(1)
Net other-than-temporary impairment losses recognized in earnings	(2)	(1)
Other
Other-than-temporary impairment losses by asset type
Total other-than-temporary impairment losses	2	(1)
Net other-than-temporary impairment losses recognized in earnings	$ 2	$ (1)