Investment Income And Gains and Losses (Total Investment Income From All Operations) (Details) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gross investment income	$ 109		$ 135		$ 352		$ 394
Investment expenses			2				4
Net investment income	109		133		352		390
Total net realized gains (losses)	(11)	[1]	50	[1]	(8)	[1]	6	[1]
Total investment income	98		183		344		396
Realized gains on trading securities	2				5
Fixed-Maturity Investments [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gross investment income	87		104		279		313
Gains	46	[2]	55		117	[2]	90
Losses	(56)		(5)		(133)		(84)
Total net realized gains (losses)	(10)		50		(16)		6
Held-To-Maturity [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gross investment income	1		2		5		5
Other Long Term Investments [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gross investment income	3		5		10		17
Gains					9		1
Losses	(1)				(1)		(1)
Total net realized gains (losses)	(1)				8
Variable Interest Entity, Primary Beneficiary [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gross investment income	17		21		53		51
Short-Term Investments [Member]
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Gross investment income	$ 1		$ 3		$ 5		$ 8

[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.

[2] Includes net trading gains of $2 million and $5 million for the three and nine months ended September 30, 2011, respectively.