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, 2017		$ 284	$ 3,171	$ 1,095	$ (19)	$ (3,118)	$ 1,413	$ 12
Balance (in common stock shares) at Dec. 31, 2017		283,717,973
Balance (in treasury stock shares) at Dec. 31, 2017						(192,233,526)
Cumulative effect of prospective application of new accounting principle | ASU 2016-13 [Member]				0
Cumulative effect of prospective application of new accounting principle | ASU 2016-01 [Member]				164	(164)
Cumulative effect of prospective application of new accounting principle | ASU 2018-02 [Member]				3	(3)
Net income (loss)	$ (296)			(296)
Other comprehensive income (loss)	$ 30				30
Treasury shares issued for warrant exercises			(21)			$ 34
Treasury shares issued for warrant exercises (in shares)						1,277,620
Treasury shares acquired under share repurchase program						$ (48)
Treasury shares acquired under share repurchase program (in shares)	(5,800,000)					(5,842,567)
Share-based compensation			(125)			$ 132
Share-based compensation (in shares)		(92,284)				2,994,497
Period change		$ 0					(294)	1
Total equity balance at Dec. 31, 2018	$ 1,132	$ 284	3,025	966	(156)	$ (3,000)	1,119	$ 13
Balance (in common stock shares) at Dec. 31, 2018		283,625,689
Balance (in treasury stock shares) at Dec. 31, 2018						(193,803,976)
Balance (in preferred stock shares) at Dec. 31, 2018								1,315
Cumulative effect of prospective application of new accounting principle | ASU 2016-13 [Member]				0
Cumulative effect of prospective application of new accounting principle | ASU 2016-01 [Member]				0	0
Cumulative effect of prospective application of new accounting principle | ASU 2018-02 [Member]				0	0
Net income (loss)	(359)			(359)
Other comprehensive income (loss)	$ 154				154
Treasury shares issued for warrant exercises			0			$ 0
Treasury shares issued for warrant exercises (in shares)						0
Treasury shares acquired under share repurchase program						$ (101)
Treasury shares acquired under share repurchase program (in shares)	(11,100,000)					(11,098,995)
Share-based compensation			(26)			$ 40
Share-based compensation (in shares)		(192,288)				902,863
Period change		$ (1)					(293)	$ 0
Total equity balance at Dec. 31, 2019	$ 839	$ 283	2,999	607	(2)	$ (3,061)	826	$ 13
Balance (in common stock shares) at Dec. 31, 2019	283,433,401	283,433,401
Balance (in treasury stock shares) at Dec. 31, 2019	(204,000,108)					(204,000,108)
Balance (in preferred stock shares) at Dec. 31, 2019	0							1,315
Cumulative effect of prospective application of new accounting principle | ASU 2016-13 [Member]				(42)
Cumulative effect of prospective application of new accounting principle | ASU 2016-01 [Member]				0	0
Cumulative effect of prospective application of new accounting principle | ASU 2018-02 [Member]				0	0
Net income (loss)	$ (578)			(578)
Other comprehensive income (loss)	$ 117				117
Treasury shares issued for warrant exercises			0			$ 0
Treasury shares issued for warrant exercises (in shares)						0
Treasury shares acquired under share repurchase program						$ (198)
Treasury shares acquired under share repurchase program (in shares)	(26,400,000)					(26,430,768)
Share-based compensation			(37)			$ 48
Share-based compensation (in shares)		(247,286)				921,909
Period change		$ 0					(690)	$ 0
Total equity balance at Dec. 31, 2020	$ 149	$ 283	$ 2,962	$ (13)	$ 115	$ (3,211)	$ 136	$ 13
Balance (in common stock shares) at Dec. 31, 2020	283,186,115	283,186,115
Balance (in treasury stock shares) at Dec. 31, 2020	(229,508,967)					(229,508,967)
Balance (in preferred stock shares) at Dec. 31, 2020	0							1,315