Investments and Derivative Instruments (Details 17) (Fair value hedges [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative	$ 17	$ 16
Gain or (Loss) Recognized in Income, Hedged Item	(16)	(15)
Interest rate swaps [Member] | Net realized capital gains (losses) [Member]
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative	11	10
Gain or (Loss) Recognized in Income, Hedged Item	(10)	(9)
Foreign currency swaps [Member] | Net realized capital gains (losses) [Member]
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative	9	14
Gain or (Loss) Recognized in Income, Hedged Item	(9)	(14)
Foreign currency swaps [Member] | Benefits, losses and loss adjustment expenses [Member]
Derivative Instruments Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income, Derivative	(3)	(8)
Gain or (Loss) Recognized in Income, Hedged Item	$ 3	$ 8