Consolidated Statements Of Changes In Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Total Shareholders' Equity Of MBIA Inc. [Member]	Preferred Stock [Member]
Total equity balance at Dec. 31, 2019		$ 283	$ 2,999	$ 607	$ (2)	$ (3,061)	$ 826
Balance (in treasury stock shares) at Dec. 31, 2019						(204,000,108)
Cumulative effect of prospective application of new accounting principle | ASU 2016-13 [Member]				(42)
Net income (loss)	$ (497)			(497)
Other comprehensive income (loss)	132				132
Treasury shares acquired under share repurchase program						$ (198)
Treasury shares acquired under share repurchase program (in shares)						(26,430,768)
Other						$ 48
Others (in shares)						924,913
Period change			(39)				(596)
Total equity balance at Sep. 30, 2020	243		2,960	68	130	$ (3,211)	230	$ 13
Balance (in common stock shares) at Sep. 30, 2020		283,433,401
Balance (in treasury stock shares) at Sep. 30, 2020						(229,505,963)
Balance (in preferred stock shares) at Sep. 30, 2020								1,315
Total equity balance at Jun. 30, 2020		$ 283	2,959	126	129	$ (3,149)	348
Balance (in treasury stock shares) at Jun. 30, 2020						(220,924,081)
Cumulative effect of prospective application of new accounting principle | ASU 2016-13 [Member]				0
Net income (loss)	(58)			(58)
Other comprehensive income (loss)	1				1
Treasury shares acquired under share repurchase program						$ (62)
Treasury shares acquired under share repurchase program (in shares)						(8,582,686)
Other						$ 0
Others (in shares)						804
Period change			1				(118)
Total equity balance at Sep. 30, 2020	243		2,960	68	130	$ (3,211)	230	$ 13
Balance (in common stock shares) at Sep. 30, 2020		283,433,401
Balance (in treasury stock shares) at Sep. 30, 2020						(229,505,963)
Balance (in preferred stock shares) at Sep. 30, 2020								1,315
Total equity balance at Dec. 31, 2020	$ 149	$ 283	2,962	(13)	115	$ (3,211)	136
Balance (in treasury stock shares) at Dec. 31, 2020	(229,508,967)					(229,508,967)
Cumulative effect of prospective application of new accounting principle | ASU 2016-13 [Member]				0
Net income (loss)	$ (290)			(290)
Other comprehensive income (loss)	(25)				(25)
Treasury shares acquired under share repurchase program						$ 0
Treasury shares acquired under share repurchase program (in shares)						0
Other						$ 35
Others (in shares)						728,928
Period change			(26)				(306)
Total equity balance at Sep. 30, 2021	$ (157)		2,936	(303)	90	$ (3,176)	(170)	$ 13
Balance (in common stock shares) at Sep. 30, 2021	283,186,115	283,186,115
Balance (in treasury stock shares) at Sep. 30, 2021	(228,780,039)					(228,780,039)
Balance (in preferred stock shares) at Sep. 30, 2021	0							1,315
Total equity balance at Jun. 30, 2021		$ 283	2,934	(180)	103	$ (3,176)	(36)
Balance (in treasury stock shares) at Jun. 30, 2021						(228,780,540)
Cumulative effect of prospective application of new accounting principle | ASU 2016-13 [Member]				0
Net income (loss)	$ (123)			(123)
Other comprehensive income (loss)	(13)				(13)
Treasury shares acquired under share repurchase program						$ 0
Treasury shares acquired under share repurchase program (in shares)						0
Other						$ 0
Others (in shares)						501
Period change			2				(134)
Total equity balance at Sep. 30, 2021	$ (157)		$ 2,936	$ (303)	$ 90	$ (3,176)	$ (170)	$ 13
Balance (in common stock shares) at Sep. 30, 2021	283,186,115	283,186,115
Balance (in treasury stock shares) at Sep. 30, 2021	(228,780,039)					(228,780,039)
Balance (in preferred stock shares) at Sep. 30, 2021	0							1,315