Consolidated Statement Of Changes In Shareholders' Equity - USD ($) $ in Millions	Total	Preferred Stock [Member]	Total Shareholders' Equity Of MBIA Inc. [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Total equity balance at Dec. 31, 2017			$ 1,413		$ 3,171	$ 1,095	$ (19)	$ (3,118)
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 2016-01 [Member]						164	(164)
Cumulative effect of prospective application of new accounting principle | ASU 2018-02 [Member]						3	(3)
Net income (loss)	$ (289)					(289)
Total other comprehensive income (loss)	(20)						(20)
Treasury shares issued					(21)			$ 34
Treasury shares issued (in shares)								1,277,620
Treasury shares acquired								$ (14)
Treasury shares acquired (in shares)								(1,961,711)
Share-based compensation, net of tax					5			$ 0
Share-based compensation (in shares)				(92,284)				(18,412)
Period change			(305)
Total equity balance at Sep. 30, 2018	1,120	$ 12	1,108	$ 284	3,155	973	(206)	$ (3,098)
Balance (in common stock shares) at Sep. 30, 2018				283,625,689
Balance (in treasury stock shares) at Sep. 30, 2018								(192,936,029)
Balance (in preferred stock shares) at Sep. 30, 2018		1,315
Total equity balance at Jun. 30, 2018			1,103		3,154	1,018	(255)	$ (3,098)
Balance (in common stock shares) at Jun. 30, 2018				283,625,689
Balance (in treasury stock shares) at Jun. 30, 2018								(192,963,698)
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)	(45)					(45)
Total other comprehensive income (loss)	49						49
Treasury shares issued					0			$ 0
Treasury shares issued (in shares)								0
Treasury shares acquired								$ 0
Treasury shares acquired (in shares)								0
Share-based compensation, net of tax					1			$ 0
Share-based compensation (in shares)				0				27,669
Period change			5
Total equity balance at Sep. 30, 2018	1,120	$ 12	1,108	$ 284	3,155	973	(206)	$ (3,098)
Balance (in common stock shares) at Sep. 30, 2018				283,625,689
Balance (in treasury stock shares) at Sep. 30, 2018								(192,936,029)
Balance (in preferred stock shares) at Sep. 30, 2018		1,315
Total equity balance at Dec. 31, 2018	$ 1,132		1,119		3,025	966	(156)	$ (3,000)
Balance (in common stock shares) at Dec. 31, 2018	283,625,689			283,625,689
Balance (in treasury stock shares) at Dec. 31, 2018	(193,803,976)							(193,803,976)
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)	$ (116)					(116)
Total other comprehensive income (loss)	113						113
Treasury shares issued					0			$ 0
Treasury shares issued (in shares)								0
Treasury shares acquired								$ (93)
Treasury shares acquired (in shares)								(10,273,891)
Share-based compensation, net of tax					(28)			$ 40
Share-based compensation (in shares)				0				920,108
Period change			(84)
Total equity balance at Sep. 30, 2019	$ 1,048	$ 13	1,035	$ 284	2,997	850	(43)	$ (3,053)
Balance (in common stock shares) at Sep. 30, 2019	283,625,689			283,625,689
Balance (in treasury stock shares) at Sep. 30, 2019	(203,157,759)							(203,157,759)
Balance (in preferred stock shares) at Sep. 30, 2019	0	1,315
Total equity balance at Jun. 30, 2019			1,040		2,995	779	(4)	$ (3,014)
Balance (in common stock shares) at Jun. 30, 2019				283,625,689
Balance (in treasury stock shares) at Jun. 30, 2019								(198,824,693)
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)	$ 71					71
Total other comprehensive income (loss)	(39)						(39)
Treasury shares issued					0			$ 0
Treasury shares issued (in shares)								0
Treasury shares acquired								$ (39)
Treasury shares acquired (in shares)								(4,341,232)
Share-based compensation, net of tax					2			$ 0
Share-based compensation (in shares)				0				8,166
Period change			(5)
Total equity balance at Sep. 30, 2019	$ 1,048	$ 13	$ 1,035	$ 284	$ 2,997	$ 850	$ (43)	$ (3,053)
Balance (in common stock shares) at Sep. 30, 2019	283,625,689			283,625,689
Balance (in treasury stock shares) at Sep. 30, 2019	(203,157,759)							(203,157,759)
Balance (in preferred stock shares) at Sep. 30, 2019	0	1,315