Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Premiums, fees and reimbursements received	$ 86	$ 61	$ 115
Investment income received	205	248	318
Insured derivative commutations and losses paid	(56)	(52)	(43)
Financial guarantee losses and loss adjustment expenses paid	(385)	(768)	(351)
Proceeds from recoveries and reinsurance	61	170	99
Operating and employee related expenses paid	(83)	(130)	(134)
Interest paid, net of interest converted to principal	(146)	(177)	(148)
Income taxes (paid) received	(1)	(4)	(5)
Net cash provided (used) by operating activities	(319)	(652)	(149)
Cash flows from investing activities:
Purchases of available-for-sale investments	(2,265)	(1,811)	(2,661)
Sales of available-for-sale investments	2,117	2,256	2,412
Paydowns and maturities of available-for-sale investments	329	568	680
Purchases of investments at fair value	(189)	(263)	(199)
Sales, paydowns and maturities of investments at fair value	212	326	260
Sales, paydowns and maturities (purchases) of short-term investments, net	420	(67)	(125)
Sales, paydowns and maturities of held-to-maturity investments	0	0	1,799
Paydowns and maturities of loans receivable and other instruments at fair value	614	259	261
Consolidation of variable interest entities	0	18	9
Deconsolidation of variable interest entities	(7)	0	(8)
(Payments) proceeds for derivative settlements	(24)	(64)	(44)
Collateral (to) from counterparties	0	4	49
Capital expenditures	(1)	(1)	(1)
Other investing	0	(23)	(8)
Net cash provided (used) by investing activities	1,206	1,202	2,424
Cash flows from financing activities:
Proceeds from investment agreements	12	17	19
Principal paydowns of investment agreements	(37)	(75)	(85)
Principal paydowns of medium-term notes	(85)	(157)	(120)
Proceeds from the MBIA Corp. Financing Facility	0	328	0
Principal paydowns of variable interest entity notes	(598)	(368)	(2,234)
Purchases of treasury stock	(44)	(330)	(110)
Other financing	0	(4)	(5)
Net cash provided (used) by financing activities	(752)	(589)	(2,535)
Effect of exchange rate changes on cash and cash equivalents	(1)	(2)	(2)
Net increase (decrease) in cash and cash equivalents	134	(41)	(262)
Cash and cash equivalents - beginning of period	146	187	522
Reclassification to assets held for sale	0	0	(73)
Cash and cash equivalents - end of period	280	146	187
Reconciliation of net income (loss) to net cash provided (used) by operating activities: [Abstract]
Net income (loss)	(296)	(1,605)	(338)
Change in: [Abstract]
Premiums receivable	60	49	75
Deferred acquisition costs	21	22	41
Unearned premium revenue	(165)	(206)	(263)
Loss and loss adjustment expense reserves	(46)	778	29
Insurance loss recoverable	(213)	(681)	(74)
Accrued interest payable	157	116	102
Accrued expenses	(9)	(29)	7
Net investment losses related to other-than-temporary impairments	5	106	5
Unrealized (gains) losses on insured derivatives	(31)	0	(21)
Net (gains) losses on financial instruments at fair value and foreign exchange	(8)	(106)	(84)
Other net realized (gains) losses	171	(59)	282
Deferred income tax provision (benefit)	0	940	(5)
Interest on variable interest entities, net	17	35	57
Other operating	18	(12)	38
Total adjustments to net income (loss)	(23)	953	189
Net cash provided (used) by operating activities	(319)	(652)	(149)
Supplementary Disclosure of Consolidated Cash Flow Information
Non-cash consideration received from the sale of MBIA UK Insurance Limited	$ 0	$ 332	$ 0