Financial Guaranty Contracts Accounted for as Credit Derivatives (Details 5) (USD $)	6 Months Ended
	Jun. 30, 2011 RatingCategories Subsidiaries Securities Policies D Companies Agreements Markets Transactions FiscalQuarters Counterparties Entities	Mar. 31, 2011	Dec. 31, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2009
Credit Spread Effect on Credit Derivatives Fair Value
Before considering implication of the Company's credit spreads	$ (5,425,100,000)	$ (5,581,400,000)	$ (5,543,900,000)	$ (5,636,300,000)	$ (5,253,500,000)	$ (5,830,800,000)
After considering implication of the Company's credit spreads	(2,184,300,000)	(2,142,200,000)	(1,872,600,000)	(1,274,900,000)	(1,284,900,000)	(1,542,100,000)
Components of Credit Derivative Assets (Liabilities)
Credit derivative assets	603,867,000		592,898,000
Credit derivative liabilities	(2,788,218,000)		(2,465,520,000)
Net fair value of credit derivatives	(2,184,300,000)		(1,872,600,000)
Other credit derivative disclosures
Gain from tightening of general market spreads as well as a run-off in net par outstanding	110,800,000
Par insured that could be terminated if ratings were downgraded	2,700,000
Number of ISDA master agreements	3
Par insured that could be terminated if ratings were downgraded to BBB- or Baa3	89,000,000
Number of counterparties that could terminate for ratings downgrade to BBB- or Baa3	1
Par insured that could be terminated if ratings were downgraded to BB+ or Ba1	2,600,000,000
Number of counterparties that could terminate for ratings downgrade to BB+ or Ba1	2
Amount of par subject to collateral posting	15,800,000,000
Collateral agreed to be posted	768,600,000
Amount of par subject to collateral for which the amount of collateral is capped	15,200,000,000
Cap on collateral requirement at current ratings levels	635,000,000
Increase to cap on collateral requirement if ratings are downgraded to A+ or A3	50,000,000
Cap on collateral requirement if ratings are downgraded to A+ or A3	$ 685,000,000
AGC
Credit Derivatives
Quoted price of CDS contract (in basis points)	6.34%	7.24%	8.04%	10.10%	7.34%	6.34%
AGM
Credit Derivatives
Quoted price of CDS contract (in basis points)	4.72%	6.60%	6.50%	8.02%	4.68%	5.41%