Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, $ in Millions		5 Months Ended	12 Months Ended
		Dec. 31, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Basic and diluted earnings per share:
Net income (loss) from continuing operations available to common shareholders - Basic			$ (149)	$ (445)	$ (578)
Net income (loss) from continuing operations available to common shareholders - Diluted			(149)	(445)	(578)
Income (loss) from discontinued operations, net of income taxes		$ (54)	(54)	0	0
Net income (loss) from discontinued operations attributable to noncontrolling interests			(8)	0	0
Net income (loss) from discontinued operations attributable to MBIA Inc.			(46)	0	0
Net income (loss) attributable to MBIA Inc.			$ (195)	$ (445)	$ (578)
Basic weighted average shares	[1]		49,803,739	49,472,281	59,071,843
Diluted weighted average shares	[1]		49,803,739	49,472,281	59,071,843
Continuing operations - Basic			$ (3)	$ (8.99)	$ (9.78)
Continuing operations - Diluted			(3)	(8.99)	(9.78)
Discontinued operations - Basic			(0.92)	0	0
Discontinued operations - Diluted			(0.92)	0	0
Net income (loss) per share attributable to MBIA Inc. - basic			(3.92)	(8.99)	(9.78)
Net income (loss) per share attributable to MBIA Inc. - diluted			$ (3.92)	$ (8.99)	$ (9.78)
Potentially dilutive securities excluded from the calculation of diluted EPS because of antidilutive affect			5,000,000	5,100,000	4,600,000

[1] Includes 0.8 million, 0.9 million and 0.9 million of participating securities that met the service condition and were eligible to receive nonforfeitable dividends or dividend equivalents for each of the years ended December 31, 2022, 2021 and 2020, respectively.