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)	$ (439)			(439)
Other comprehensive income (loss)	131				131
Treasury shares acquired under share repurchase program						$ (136)
Treasury shares acquired under share repurchase program (in shares)						(17,848,082)
Other						$ 48
Others (in shares)						924,109
Period change			(41)				(479)
Total equity balance at Jun. 30, 2020	360		2,958	126	129	$ (3,149)	347	$ 13
Balance (in common stock shares) at Jun. 30, 2020		283,433,401
Balance (in treasury stock shares) at Jun. 30, 2020						(220,924,081)
Balance (in preferred stock shares) at Jun. 30, 2020								1,315
Total equity balance at Mar. 31, 2020		$ 283	2,961	232	91	$ (3,083)	484
Balance (in treasury stock shares) at Mar. 31, 2020						(211,272,995)
Cumulative effect of prospective application of new accounting principle | ASU 2016-13 [Member]				0
Net income (loss)	(106)			(106)
Other comprehensive income (loss)	38				38
Treasury shares acquired under share repurchase program						$ (71)
Treasury shares acquired under share repurchase program (in shares)						(9,765,326)
Other						$ 5
Others (in shares)						114,240
Period change			(3)				(137)
Total equity balance at Jun. 30, 2020	360		2,958	126	129	$ (3,149)	347	$ 13
Balance (in common stock shares) at Jun. 30, 2020		283,433,401
Balance (in treasury stock shares) at Jun. 30, 2020						(220,924,081)
Balance (in preferred stock shares) at Jun. 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)	$ (167)			(167)
Other comprehensive income (loss)	(12)				(12)
Treasury shares acquired under share repurchase program						$ 0
Treasury shares acquired under share repurchase program (in shares)						0
Other						$ 35
Others (in shares)						728,427
Period change			(28)				(172)
Total equity balance at Jun. 30, 2021	$ (23)		2,934	(180)	103	$ (3,176)	(36)	$ 13
Balance (in common stock shares) at Jun. 30, 2021	283,186,115	283,186,115
Balance (in treasury stock shares) at Jun. 30, 2021	(228,780,540)					(228,780,540)
Balance (in preferred stock shares) at Jun. 30, 2021	0							1,315
Total equity balance at Mar. 31, 2021		$ 283	2,934	(119)	39	$ (3,179)	(42)
Balance (in treasury stock shares) at Mar. 31, 2021						(228,837,465)
Cumulative effect of prospective application of new accounting principle | ASU 2016-13 [Member]				0
Net income (loss)	$ (61)			(61)
Other comprehensive income (loss)	64				64
Treasury shares acquired under share repurchase program						$ 0
Treasury shares acquired under share repurchase program (in shares)						0
Other						$ 3
Others (in shares)						56,925
Period change			0				6
Total equity balance at Jun. 30, 2021	$ (23)		$ 2,934	$ (180)	$ 103	$ (3,176)	$ (36)	$ 13
Balance (in common stock shares) at Jun. 30, 2021	283,186,115	283,186,115
Balance (in treasury stock shares) at Jun. 30, 2021	(228,780,540)					(228,780,540)
Balance (in preferred stock shares) at Jun. 30, 2021	0							1,315