Consolidated Statement Of Changes In Shareholders' Equity (USD $) In Millions, except Share data, unless otherwise specified	MBIA Inc. [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Preferred Stock Of Subsidiary And Noncontrolling Interest [Member]	Total
Balance at Dec. 31, 2008	$ 994	$ 273	$ 3,051	$ 1,629	$ (1,776)	$ (2,183)	$ 28
Balance (in shares) at Dec. 31, 2008		273,199,801				(65,278,904)	2,759
ASC 944-20 transition adjustment, net of tax of $27	55			55
ASC 320-10 transition adjustment, net of tax of $30	30			86	(56)
Comprehensive income (loss):
Net income (loss)	634			634				634
Other comprehensive income (loss):
Change in unrealized gains and losses on investments, net of tax	1,075				1,075
Portion of other-than-temporary impairment losses recognized in other comprehensive loss, net of tax	(264)				(264)
Change in fair value of derivative instruments, net of tax	85				85
Change in foreign currency translation, net of tax	(5)				(5)
Other comprehensive income (loss)	891
Total comprehensive income (loss)	1,525
Share-based compensation, net of tax (in shares)		1,627,071				85,280
Share-based compensation, net of tax	12	2	7			3
Treasury shares acquired under share repurchase program (in shares)						(4,965,400)
Treasury shares acquired under share repurchase program	(15)					(15)
Preferred shares of subsidiary acquired (in shares)							(1,082)
Preferred shares of subsidiary acquired							(11)
Preferred stock dividends of subsidiary	(11)			(11)				(11)
Significant Accounting Policies:
Change in unrealized gains and losses and other-than-temporary impairments on investments arising during the period, net of tax								283
Reclassification adjustment, net of tax								528
Change in net unrealized gains and losses and other-than-temporary impairment losses, net of taxes								811
Balance at Dec. 31, 2009	2,590	275	3,058	2,393	(941)	(2,195)	17
Balance (in shares) at Dec. 31, 2009		274,826,872				(70,159,024)	1,677
ASU 2009-17 transition adjustment:
Consolidated variable interest entities, net of tax of $23	(55)			(319)	264
Deconsolidated variable interest entities, net of tax of $2	82			(3)	85
Total ASU 2009-17 transition adjustment	27			(322)	349
Comprehensive income (loss):
Net income (loss)	53			53				53
Other comprehensive income (loss):
Change in unrealized gains and losses on investments, net of tax	322				322
Portion of other-than-temporary impairment losses recognized in other comprehensive loss, net of tax	(7)				(7)
Change in fair value of derivative instruments, net of tax	14				14
Change in foreign currency translation, net of tax	(143)				(143)
Other comprehensive income (loss)	186
Total comprehensive income (loss)	239
Share-based compensation, net of tax (in shares)		(107,294)				(78,654)
Share-based compensation, net of tax	7		6			1
Treasury shares acquired under share repurchase program (in shares)						(4,736,300)
Treasury shares acquired under share repurchase program	(31)					(31)
Preferred shares of subsidiary acquired (in shares)							(251)
Preferred shares of subsidiary acquired							(3)
Significant Accounting Policies:
Change in unrealized gains and losses and other-than-temporary impairments on investments arising during the period, net of tax								121
Reclassification adjustment, net of tax								194
Change in net unrealized gains and losses and other-than-temporary impairment losses, net of taxes								315
Balance at Dec. 31, 2010	2,832	275	3,064	2,124	(406)	(2,225)	14	2,832
Balance (in shares) at Dec. 31, 2010		274,719,578				(74,973,978)	1,426
Comprehensive income (loss):
Net income (loss)	(1,319)			(1,319)				(1,319)
Other comprehensive income (loss):
Change in unrealized gains and losses on investments, net of tax	252				252
Portion of other-than-temporary impairment losses recognized in other comprehensive loss, net of tax	6				6
Change in fair value of derivative instruments, net of tax	5				5
Change in foreign currency translation, net of tax	(33)				(33)
Other comprehensive income (loss)	230
Total comprehensive income (loss)	(1,089)
Share-based compensation, net of tax (in shares)		176,584				(237,912)
Share-based compensation, net of tax	7		8			(1)
Treasury shares acquired under share repurchase program (in shares)						(6,541,076)
Treasury shares acquired under share repurchase program	(50)					(50)
Preferred shares of subsidiary acquired (in shares)							(111)
Preferred shares of subsidiary acquired							(2)
Change in noncontrolling interest in subsidiary							11
Significant Accounting Policies:
Change in unrealized gains and losses and other-than-temporary impairments on investments arising during the period, net of tax								218
Reclassification adjustment, net of tax								40
Change in net unrealized gains and losses and other-than-temporary impairment losses, net of taxes								258
Balance at Dec. 31, 2011	$ 1,700	$ 275	$ 3,072	$ 805	$ (176)	$ (2,276)	$ 23	$ 1,700
Balance (in shares) at Dec. 31, 2011		274,896,162				(81,752,966)	1,315