Investments and Derivative Instruments (Details 17) (Fair value hedges [Member], USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative	$ (6)	$ (58)	$ 10	$ (95)
Gain or (Loss) Recognized in Income, Hedge Item	5	56	(10)	91
Interest rate swaps [Member] | Net realized capital gains [Member]
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative	(27)	(40)	(17)	(52)
Gain or (Loss) Recognized in Income, Hedge Item	26	37	17	47
Interest rate swaps [Member] | Benefits, losses and loss adjustment expenses [Member]
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative		(7)		(2)
Gain or (Loss) Recognized in Income, Hedge Item		8		3
Foreign currency swaps [Member] | Net realized capital gains [Member]
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative	22	(11)	36	(40)
Gain or (Loss) Recognized in Income, Hedge Item	(22)	11	(36)	40
Foreign currency swaps [Member] | Benefits, losses and loss adjustment expenses [Member]
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative	(1)		(9)	(1)
Gain or (Loss) Recognized in Income, Hedge Item	$ 1		$ 9	$ 1