Insurance In Force (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Insurance In Force [Line Items]
Transactions guaranteed by MBIA on behalf of various investment management service affiliates	$ 4,400,000,000	$ 4,900,000,000
Credit derivative contracts	1,300,000,000
Amount available under these letters of credit and trust arrangements	7,000,000
Aggregate amount of insurance in force ceded to reinsurers	7,500,000,000	9,800,000,000
Third party reinsurance	9,100,000,000	10,400,000,000
Amount of insurance in force for FGIC policies	16,100,000,000	18,300,000,000
Aggregate amount of insured par outstanding ceded to reinsurers	4,269,000,000	5,700,000,000
Recoveries received on claims for financial guarantee policies under reinsurance contracts	10,000,000	21,000,000	41,000,000
Ceding commissions from reinsurance	3,000,000	7,000,000	6,000,000
Maximum [Member]
Insurance In Force [Line Items]
Insurance in force, expected maturity range, years	46
Minimum [Member]
Insurance In Force [Line Items]
Insurance in force, expected maturity range, years	1
Guarantees Of Derivative Contracts [Member]
Insurance In Force [Line Items]
Maximum amount of future guarantee payments	73,100,000,000
Guarantees of derivative contracts, maturity range, maximum (Years)	1
Guarantees of derivative contracts, maturity range, minimum (Years)	71
Derivative liabilities	4,800,000,000	4,400,000,000
Investment Agreement Contracts [Member]
Insurance In Force [Line Items]
Maximum amount of future guarantee payments	$ 4,400,000,000
Guarantees of derivative contracts, maturity range, maximum (Years)	1
Guarantees of derivative contracts, maturity range, minimum (Years)	36