Debt (Long-Term Debt) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2014		Jan. 16, 2008
Debt Instrument [Line Items]
Long-term debt, gross		$ 582		$ 592
Surplus notes outstanding		940	[1]	940	[1]	$ 1,000
Total		1,908		1,810
6.400% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	[2]	$ 266		266
Long-term debt, interest rate		6.40%
Long-term debt, maturity year		2022
Initial Callable date		Aug. 15, 2006
7.000% Debentures Due 2025 [Member]
Debt Instrument [Line Items]
Long-term debt, gross		$ 46		56
Long-term debt, interest rate		7.00%
Long-term debt, maturity year		2025
7.150% Debentures Due 2027 [Member]
Debt Instrument [Line Items]
Long-term debt, gross		$ 100		100
Long-term debt, interest rate		7.15%
Long-term debt, maturity year		2027
6.625% Debentures Due 2028 [Member]
Debt Instrument [Line Items]
Long-term debt, gross		$ 141		141
Long-term debt, interest rate		6.625%
Long-term debt, maturity year		2028
5.700% Senior Notes Due 2034 [Member]
Debt Instrument [Line Items]
Long-term debt, gross	[3]	$ 21		21
Long-term debt, interest rate		5.70%
Long-term debt, maturity year		2034
14% Surplus Notes Due 2033 [Member]
Debt Instrument [Line Items]
Accrued interest		$ 386		278
Long-term debt, interest rate		14.00%
Long-term debt, maturity year		2033
Callable date for fifth anniversary of initial callable date		Jan. 15, 2018
MBIA Inc Senior Notes [Member]
Debt Instrument [Line Items]
Accrued interest		$ 8		$ 8

[1] Callable on or after January 15, 2018 and every fifth anniversary thereafter at 100.00.

[2] Callable on or after August 15, 2006 at 100.00.

[3] Callable anytime at the greater of 100.00 or the present value of the remaining scheduled payments of principal and interest.