Fair Value Of Financial Instruments (Gains And Losses (Realized And Unrealized) Included In Earnings Pertaining To Level 3 Assets And Liabilities) (Details) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gains (Losses) on Insured Derivatives	$ 776		$ (1,044)		$ (531)		$ (1,717)
Net Realized Gain (Losses)	(11)	[1]	50	[1]	(8)	[1]	6	[1]
Net Gains (Losses) on Financial Instruments at Fair value and Foreign Exchange	13		12		(114)		(36)
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Inputs, Level 3 [Member] | Total Gains (Losses) Included In Earnings [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Realized Gain (Losses)
Net Gains (Losses) on Financial Instruments at Fair value and Foreign Exchange	328		(15)		235		59
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Inputs, Level 3 [Member] | Change In Unrealized Gains (Losses) For The Period Included In Earnings For Assets And Liabilities Still Held [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Realized Gain (Losses)
Net Gains (Losses) on Financial Instruments at Fair value and Foreign Exchange	331		(15)		281		59
Fair Value, Inputs, Level 3 [Member] | Total Gains (Losses) Included In Earnings [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gains (Losses) on Insured Derivatives	777		(1,046)		(530)		(1,719)
Net Realized Gain (Losses)	(79)		519		(683)		374
Net Gains (Losses) on Financial Instruments at Fair value and Foreign Exchange	77		3		(12)		2
Fair Value, Inputs, Level 3 [Member] | Change In Unrealized Gains (Losses) For The Period Included In Earnings For Assets And Liabilities Still Held [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized Gains (Losses) on Insured Derivatives	388		(531)		(2,160)		(1,208)
Net Gains (Losses) on Financial Instruments at Fair value and Foreign Exchange	73		(7)		(6)		(1)
Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net Gains (Losses) on Financial Instruments at Fair value and Foreign Exchange	$ 88		$ (19)		$ 3		$ 394

[1] Reported within the "Net gains (losses) on financial instruments at fair value and foreign exchange" and "Net investment losses related to other-than-temporary impairments" line items on MBIA's consolidated statements of operations.