Investment Income And Gains And Losses (Total Investment Income From All Operations) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gross investment income	$ 457		$ 531		$ 662
Investment expenses	4		1		6
Net investment income	453		530		656
Total net realized gains (losses)	30	[1]	(1)	[1]	(480)	[1]
Total investment income	483		529		176
Realized gains on trading securities	9
Fixed-Maturity Investments [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gross investment income	357		407		511
Gains	252	[2]	112	[2]	160	[2]
Losses	(224)		(112)		(447)
Total net realized gains (losses)	28				(287)
Held-To-Maturity [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gross investment income	6		7		9
Other Long Term Investments [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gross investment income	19		22		32
Gains	12				28
Losses	(10)		(1)		(124)
Total net realized gains (losses)	2		(1)		(96)
Variable Interest Entities [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gross investment income	69		73		89
Gains					12
Losses					(109)
Total net realized gains (losses)					(97)
Short-Term Investments [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gross investment income	$ 6		$ 22		$ 21

[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.

[2] Includes net trading gains of$9 million for the year ended December 31, 2011.