Investments and Derivative Instruments (Details 17) (Fair value hedges [Member], USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative	$ (87)	$ 13	$ (77)	$ (82)
Gain or (Loss) Recognized in Income, Hedge Item	87	(12)	77	79
Interest rate swaps [Member] | Net realized capital gain/(loss) [Member]
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative	(54)	(25)	(71)	(77)
Gain or (Loss) Recognized in Income, Hedge Item	54	25	71	72
Interest rate swaps [Member] | Benefits, losses and loss adjustment expenses [Member]
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative		(1)		(3)
Gain or (Loss) Recognized in Income, Hedge Item		2		5
Foreign currency swaps [Member] | Net realized capital gain/(loss) [Member]
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative	(28)	44	8	4
Gain or (Loss) Recognized in Income, Hedge Item	28	(44)	(8)	(4)
Foreign currency swaps [Member] | Benefits, losses and loss adjustment expenses [Member]
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative	(5)	(5)	(14)	(6)
Gain or (Loss) Recognized in Income, Hedge Item	$ 5	$ 5	$ 14	$ 6