Schedule II (Condensed Balance Sheets) (Detail) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets [Abstract]
Cash and cash equivalents	$ 167	$ 83	$ 280	$ 146
Total assets	5,751	7,284
Liabilities:
Total liabilities	5,602	6,445
Equity:
Preferred stock, par value $1 per share; authorized shares—10,000,000; issued and outstanding—none	0	0
Common stock, par value $1 per share; authorized shares—400,000,000; issued shares—283,186,115 and 283,433,401	283	283
Additional paid-in capital	2,962	2,999
Retained earnings (deficit)	(13)	607
Accumulated other comprehensive income (loss), net of tax	115	(2)	(156)	(19)
Treasury stock, at cost—229,508,967 and 204,000,108 shares	(3,211)	(3,061)
Total shareholders' equity of MBIA Inc.	136	826
Total liabilities and equity	$ 5,751	$ 7,284
Preferred stock, par value	$ 1	$ 1
Preferred stock, authorized shares	10,000,000	10,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, par value	$ 1	$ 1
Common stock, authorized shares	400,000,000	400,000,000
Common stock, issued shares	283,186,115	283,433,401
Treasury stock, shares	229,508,967	204,000,108
Parent Company [Member]
Assets [Abstract]
Fixed-maturity securities held as available-for-sale, at fair value (amortized cost $621 and $610)	$ 719	$ 674
Investments carried at fair value	1	1
Investments pledged as collateral, at fair value (amortized cost $10 and $19)	1	11
Short-term investments held as available-for-sale, at fair value (amortized cost $31 and $167)	31	167
Total investments	752	853
Cash and cash equivalents	26	11	$ 40	$ 10
Investment in wholly-owned subsidiaries	728	1,456
Other assets	139	123
Total assets	1,645	2,443
Liabilities:
Investment agreements	269	274
Long-term debt	312	427
Affiliate loans payable	695	658
Income taxes payable	12	60
Derivative liabilities	164	133
Other liabilities	57	65
Total liabilities	1,509	1,617
Equity:
Preferred stock, par value $1 per share; authorized shares—10,000,000; issued and outstanding—none	0	0
Common stock, par value $1 per share; authorized shares—400,000,000; issued shares—283,186,115 and 283,433,401	283	283
Additional paid-in capital	2,962	2,999
Retained earnings (deficit)	(13)	607
Accumulated other comprehensive income (loss), net of tax	115	(2)
Treasury stock, at cost—229,508,967 and 204,000,108 shares	(3,211)	(3,061)
Total shareholders' equity of MBIA Inc.	136	826
Total liabilities and equity	1,645	2,443
Fixed-maturity securities held as available-for-sale, amortized cost	621	610
Investments pledged as collateral, amortized cost	10	19
Short-term investments, amortized cost	$ 31	$ 167
Preferred stock, par value	$ 1	$ 1
Preferred stock, authorized shares	10,000,000	10,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, par value	$ 1	$ 1
Common stock, authorized shares	400,000,000	400,000,000
Common stock, issued shares	283,186,115	283,433,401
Treasury stock, shares	229,508,967	204,000,108