Consolidated Statement Of Changes In Shareholders' Equity - 9 months ended Sep. 30, 2018 - 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	$ 1,425	$ 12	$ 1,413	$ 284	$ 3,171	$ 1,095	$ (19)	$ (3,118)
Balance (in common stock shares) at Dec. 31, 2017	283,717,973			283,717,973
Balance (in treasury stock shares) at Dec. 31, 2017	(192,233,526)							(192,233,526)
Balance (in preferred stock shares) at Dec. 31, 2017	0	1,315
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	(3)
Net income (loss)	(289)		(289)			(289)
Total other comprehensive income (loss)	(20)		(20)				(20)
Share-based compensation	5		5	$ 0	5			$ 0
Share-based compensation (in shares)				(92,284)				(18,412)
Treasury shares issued	$ 13		13		(21)			$ 34
Treasury shares issued (in shares)	1,300,000							1,277,620
Treasury shares acquired	$ (14)		(14)					$ (14)
Treasury shares acquired (in shares)								(1,961,711)
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			283,625,689
Balance (in treasury stock shares) at Sep. 30, 2018	(192,936,029)							(192,936,029)
Balance (in preferred stock shares) at Sep. 30, 2018	0	1,315