Financial Guaranty Contracts Accounted for as Credit Derivatives (Details 5) (USD $)	3 Months Ended
	Sep. 30, 2013		Dec. 31, 2012		Sep. 30, 2013 5 year spread [Member] AGC	Jun. 30, 2013 5 year spread [Member] AGC	Mar. 31, 2013 5 year spread [Member] AGC	Dec. 31, 2012 5 year spread [Member] AGC	Sep. 30, 2012 5 year spread [Member] AGC	Mar. 31, 2012 5 year spread [Member] AGC	Dec. 31, 2011 5 year spread [Member] AGC	Sep. 30, 2013 5 year spread [Member] AGM	Jun. 30, 2013 5 year spread [Member] AGM	Mar. 31, 2013 5 year spread [Member] AGM	Dec. 31, 2012 5 year spread [Member] AGM	Sep. 30, 2012 5 year spread [Member] AGM	Mar. 31, 2012 5 year spread [Member] AGM	Dec. 31, 2011 5 year spread [Member] AGM	Sep. 30, 2013 1 year spread [Member] [Member] AGC	Jun. 30, 2013 1 year spread [Member] [Member] AGC	Mar. 31, 2013 1 year spread [Member] [Member] AGC	Dec. 31, 2012 1 year spread [Member] [Member] AGC	Sep. 30, 2012 1 year spread [Member] [Member] AGC	Mar. 31, 2012 1 year spread [Member] [Member] AGC	Dec. 31, 2011 1 year spread [Member] [Member] AGC	Sep. 30, 2013 1 year spread [Member] [Member] AGM	Jun. 30, 2013 1 year spread [Member] [Member] AGM	Mar. 31, 2013 1 year spread [Member] [Member] AGM	Dec. 31, 2012 1 year spread [Member] [Member] AGM	Sep. 30, 2012 1 year spread [Member] [Member] AGM	Mar. 31, 2012 1 year spread [Member] [Member] AGM	Dec. 31, 2011 1 year spread [Member] [Member] AGM	Sep. 30, 2013 Pooled Corporate Obligations [Member]		Dec. 31, 2012 Pooled Corporate Obligations [Member]		Sep. 30, 2013 U.S. RMBS		Dec. 31, 2012 U.S. RMBS		Sep. 30, 2013 CMBS		Dec. 31, 2012 CMBS		Sep. 30, 2013 Other		Dec. 31, 2012 Other
Components of Credit Derivative Assets (Liabilities)
Quoted price of CDS contract (as a percent)					4.65%	3.43%	3.97%	6.78%	7.80%	9.04%	11.40%	5.02%	3.65%	3.80%	5.36%	6.38%	6.52%	7.78%	1.85%	0.57%	0.59%	2.70%	4.58%	6.29%	9.65%	2.15%	0.72%	0.60%	2.57%	3.33%	4.16%	5.38%
Gain from tightening of spreads	$ 854,000,000
Fair value of credit derivatives before effect of AGC and AGM credit spreads
Fair value of credit derivatives before effect of AGC and AGM credit spreads	(3,955,000,000)		(4,809,000,000)
Plus: Effect of AGC and AGM credit spreads	2,034,000,000		3,016,000,000
Net fair value of credit derivatives	(1,921,000,000)		(1,793,000,000)																														(40,000,000)		6,000,000		(1,487,000,000)		(1,237,000,000)		(3,000,000)		(2,000,000)		(391,000,000)		(560,000,000)
Present Value of Expected Claim (Payments) Recoveries	(164,000,000)	[1]	(282,000,000)	[1]																													(33,000,000)	[1]	(16,000,000)	[1]	(175,000,000)	[1]	(181,000,000)	[1]	0	[1]	0	[1]	44,000,000	[1]	(85,000,000)	[1]
Present Value of Future Installment Fees Receivable	41,000,000		43,000,000
R and W Included in Credit Derivative Asset (Liability)	174,000,000		237,000,000
Other credit derivative disclosures
Par insured that could be terminated if ratings were downgraded	1,700,000,000
Amount of par subject to collateral posting	11,200,000,000
Cap on collateral requirement at current ratings levels	10,800,000,000
Amount of par subject to collateral for which the amount of collateral is capped	675,000,000
Collateral agreed to be posted	681,000,000
Credit Derivative, Notional Amount Subject to Collateral based in MTM valuation	373,000,000
Credit Derivative, Collateral Posted, based in MTM valuation	$ 64,000,000

[1] Represents amount in excess of the present value of future installment fees to be received of $41 million as of September 30, 2013 and $43 million as of December 31, 2012. Includes R&W benefit of $174 million as of September 30, 2013 and $237 million as of December 31, 2012.