Financial Guaranty Contracts Accounted for as Credit Derivatives (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Credit Derivatives
Net unrealized gains (losses)	$ 330	$ (38)	$ (120)	$ (388)
Pooled corporate
Credit Derivatives
Net unrealized gains (losses)	96	32	(43)	62
U.S. RMBS
Credit Derivatives
Net unrealized gains (losses)	195	(78)	(248)	(457)
CMBS
Credit Derivatives
Net unrealized gains (losses)	3	0	(1)	0
Other
Credit Derivatives
Net unrealized gains (losses)	36	8	172	7
AGC R&W Benefits From Deutsche Bank Settlement
Credit Derivatives
Unrealized Gain (Loss) on Derivatives				$ 85