Fair Value Of Financial Instruments (Gains And Losses On Fair Value Option Included In The Company's Consolidated Statements Of Operations) (Detail) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015	Jun. 30, 2014
Accounts Notes And Loans Receivable [Line Items]
Net gains (losses) on financial instruments at fair value and foreign exchange		$ 45		$ 61		$ 75	$ 6
Non Variable Interest Entity [Member]
Accounts Notes And Loans Receivable [Line Items]
Net gains (losses) on financial instruments at fair value and foreign exchange		45		61		75	6
Variable Interest Entity [Member]
Accounts Notes And Loans Receivable [Line Items]
Net gains (losses) on financial instruments at fair value and foreign exchange		6		23		(4)	26
Variable Interest Entity [Member] | Loan Repurchase Commitments [Member]
Accounts Notes And Loans Receivable [Line Items]
Net gains (losses) on financial instruments at fair value and foreign exchange	[1]	3				9	5
Investments Carried At Fair Value [Member] | Non Variable Interest Entity [Member]
Accounts Notes And Loans Receivable [Line Items]
Net gains (losses) on financial instruments at fair value and foreign exchange		0	[2]	1	[2]	1	2	[2]
Fixed Maturity Securities Held At Fair Value - VIE [Member] | Variable Interest Entity [Member]
Accounts Notes And Loans Receivable [Line Items]
Net gains (losses) on financial instruments at fair value and foreign exchange	[1]	(55)		(30)		(73)	(68)
Residential Mortgage Loans [Member] | Variable Interest Entity [Member]
Accounts Notes And Loans Receivable [Line Items]
Net gains (losses) on financial instruments at fair value and foreign exchange	[1]	(54)		(17)		(113)	(73)
Medium Term Notes [Member] | Non Variable Interest Entity [Member]
Accounts Notes And Loans Receivable [Line Items]
Net gains (losses) on financial instruments at fair value and foreign exchange	[2]	13		(2)		31	(14)
Variable Interest Entity Notes [Member] | Variable Interest Entity [Member]
Accounts Notes And Loans Receivable [Line Items]
Net gains (losses) on financial instruments at fair value and foreign exchange	[1]	$ 72		$ 48		$ 162	$ 169

[1] Reported within Net gains (losses) of financial instruments at fair value and foreign exchange-VIE on MBIA's consolidated statements of operations.

[2] Reported within Net gains (losses) of financial instruments at fair value and foreign exchange on MBIA's consolidated statements of operations.