Investments (Realized gain (loss) related to certain investments) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Realized Gain Loss Related To Certain Investments [Abstract]
Fixed maturity AFS securities, Gross gains	$ 16	$ 86	$ 107
Fixed maturity AFS securities, Gross losses	(202)	(227)	(248)
Equity AFS securities, Gross gains	1	12	9
Equity AFS securities, Gross losses	(9)	0	(3)
Gain (loss) on other investments	2	(9)	(53)
Associated amortization expense of DAC, VOBA, DSI and DFEL and changes in other contract holder funds	2	(10)	8
Total realized gain (loss) related to certain investments	$ (190)	$ (148)	$ (180)