Consolidated Statements Of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Premiums, fees and reimbursements received	$ 73	$ 41
Investment income received	162	193
Insured derivative commutations and losses paid	(49)	(41)
Financial guarantee losses and loss adjustment expenses paid	(367)	(744)
Proceeds from recoveries and reinsurance	46	100
Operating and employee related expenses paid	(68)	(103)
Interest paid, net of interest converted to principal	(119)	(139)
Income taxes (paid) received	(1)	0
Net cash provided (used) by operating activities	(323)	(693)
Cash flows from investing activities:
Purchases of available-for-sale investments	(1,684)	(1,146)
Sales of available-for-sale investments	1,647	1,300
Paydowns and maturities of available-for-sale investments	245	392
Purchases of investments at fair value	(142)	(199)
Sales, paydowns and maturities of investments at fair value	162	270
Sales, paydowns and maturities (purchases) of short-term investments, net	269	67
Paydowns and maturities of loans receivable	365	202
Consolidation of variable interest entities	0	18
Deconsolidation of variable interest entities	(7)	0
(Payments) proceeds for derivative settlements	(19)	(58)
Collateral (to) from counterparties	0	4
Capital expenditures	0	(1)
Other investing	0	(23)
Net cash provided (used) by investing activities	836	826
Cash flows from financing activities:
Proceeds from investment agreements	9	13
Principal paydowns of investment agreements	(30)	(57)
Principal paydowns of medium-term notes	(62)	(55)
Proceeds from the MBIA Corp. Financing Facility	0	328
Principal paydowns of variable interest entity notes	(382)	(311)
Purchases of treasury stock	(15)	(98)
Other financing	0	(4)
Net cash provided (used) by financing activities	(480)	(184)
Net increase (decrease) in cash and cash equivalents	33	(51)
Cash and cash equivalents - beginning of period	146	187
Cash and cash equivalents - end of period	179	136
Reconciliation of net income (loss) to net cash provided (used) by operating activities: [Abstract]
Net income (loss)	(289)	(1,568)
Change in: [Abstract]
Premiums receivable	54	34
Deferred acquisition costs	18	22
Unearned premium revenue	(142)	(149)
Loss and loss adjustment expense reserves	50	615
Insurance loss recoverable	(192)	(781)
Accrued interest payable	113	81
Accrued expenses	(10)	(26)
Unrealized (gains) losses on insured derivatives	(36)	10
Net (gains) losses on financial instruments at fair value and foreign exchange	(47)	53
Other net realized (gains) losses	126	(64)
Deferred income tax provision (benefit)	1	961
Interest on variable interest entities, net	14	26
Other operating	17	93
Total adjustments to net income (loss)	(34)	875
Net cash provided (used) by operating activities	(323)	(693)
Supplementary Disclosure of Consolidated Cash Flow Information
Non-cash consideration received from the sale of MBIA UK Insurance Limited	$ 0	$ 332