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, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gains (losses) on insured derivatives	$ (441)		$ (607)		$ 1,650
Net Realized Gain (Losses)	30	[1]	(1)	[1]	(480)	[1]
Variable Interest Entities [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	59		342		(4)
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	(440)		(609)		1,380
Net Realized Gain (Losses)	(2,488)		(282)		146
Net Gains (Losses) on Financial Instruments at Fair Value and Foreign Exchange	(75)		(11)		(11)
Fair Value, Inputs, Level 3 [Member] | Total Gains (Losses) Included In Earnings [Member] | Variable Interest Entities [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	230		(340)
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	(2,702)		(1,338)		1,140
Net Gains (Losses) on Financial Instruments at Fair Value and Foreign Exchange	(86)		(3)		(11)
Fair Value, Inputs, Level 3 [Member] | Change In Unrealized Gains (Losses) For The Period Included In Earnings For Assets And Liabilities Still Held [Member] | Variable Interest Entities [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	347		(395)
Fixed Maturity Securities Held At Fair Value [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	(484)		374
Other Loans [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	(19)		(26)
Residential Mortgage Loans [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	$ (143)		$ 295

[1] These balances are included in 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.