Investments (Increase decrease in payables for collateral on investments ) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Increase Decrease In Payables For Collateral On Investments [Abstract]
Collateral payable held for derivative investments	$ (413)	$ 2,180	$ 183
Securities pledged under securities lending agreements	(3)	1	(302)
Securities pledged under reverse repurchase agreements	0	0	(64)
Securities pledged for TALF	(136)	(107)	(65)
Securities pledged for FHLBI	1,000	0	0
Total increase (decrease) in payables for collateral on investments	$ 448	$ 2,074	$ (248)