Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Premiums, fees and reimbursements received	$ 61	$ 115	$ 95
Investment income received	248	318	353
Insured derivative commutations and losses paid	(52)	(43)	(42)
Financial guarantee losses and loss adjustment expenses paid	(768)	(351)	(238)
Proceeds from recoveries and reinsurance	170	99	85
Operating and employee related expenses paid	(130)	(134)	(129)
Interest paid, net of interest converted to principal	(155)	(139)	(169)
Income taxes (paid) received	(4)	(5)	(9)
Net cash provided (used) by operating activities	(630)	(140)	(54)
Cash flows from investing activities:
Purchases of available-for-sale investments	(1,811)	(2,661)	(2,146)
Sales of available-for-sale investments	2,256	2,412	1,145
Paydowns and maturities of available-for-sale investments	568	680	800
Purchases of investments at fair value	(263)	(199)	(390)
Sales, paydowns and maturities of investments at fair value	326	260	551
Sales, paydowns and maturities (purchases) of short-term investments, net	(67)	(125)	525
Sales, paydowns and maturities of held-to-maturity investments	0	1,799	67
Paydowns and maturities of loans receivable	259	261	232
Consolidation of variable interest entities	18	9	7
Deconsolidation of variable interest entities	0	(8)	0
(Payments) proceeds for derivative settlements	(64)	(44)	13
Collateral (to) from counterparties	4	49	(31)
Capital expenditures	(1)	(1)	(3)
Other investing	(23)	(8)	47
Net cash provided (used) by investing activities	1,202	2,424	817
Cash flows from financing activities:
Proceeds from investment agreements	17	19	24
Principal paydowns of investment agreements	(84)	(85)	(116)
Principal paydowns of medium-term notes	(171)	(129)	(118)
Proceeds from the MBIA Corp. Financing Facility	328	0	0
Principal paydowns of variable interest entity notes	(368)	(2,234)	(490)
Principal paydowns of long-term debt	0	0	(11)
Purchases of treasury stock	(330)	(110)	(304)
Other financing	(3)	(5)	0
Net cash provided (used) by financing activities	(611)	(2,544)	(1,015)
Effect of exchange rate changes on cash and cash equivalents	(2)	(2)	(8)
Net increase (decrease) in cash and cash equivalents	(41)	(262)	(260)
Cash and cash equivalents - beginning of year	187	522	782
Reclassification to assets held for sale	0	(73)	0
Cash and cash equivalents - end of year	146	187	522
Reconciliation of net income (loss) to net cash provided (used) by operating activities: [Abstract]
Net income (loss)	(1,605)	(338)	180
Change in: [Abstract]
Premiums receivable	49	75	50
Deferred acquisition costs	22	41	49
Unearned premium revenue	(206)	(263)	(371)
Loss and loss adjustment expense reserves	778	29	12
Insurance loss recoverable	(681)	(74)	(44)
Accrued interest payable	138	111	105
Accrued expenses	(29)	7	14
Net investment losses related to other-than-temporary impairments	106	5	13
Unrealized (gains) losses on insured derivatives	0	(21)	(157)
Net (gains) losses on financial instruments at fair value and foreign exchange	(106)	(84)	(105)
Other net realized (gains) losses	(59)	282	(17)
Deferred income tax provision (benefit)	940	(5)	107
Interest on variable interest entities, net	35	57	71
Other operating	(12)	38	39
Total adjustments to net income (loss)	975	198	(234)
Net cash provided (used) by operating activities	(630)	(140)	(54)
Supplementary Disclosure of Consolidated Cash Flow Information
Non-cash consideration received from the sale of MBIA UK Insurance Limited	$ 332	$ 0	$ 0