Consolidated Statements Of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Premiums, fees and reimbursements received	$ 115	$ 95	$ 193
Investment income received	318	353	419
Errors and omissions insurance recoveries received	0	0	30
Insured derivative commutations and losses paid	(43)	(42)	(432)
Financial guarantee losses and loss adjustment expenses paid	(351)	(238)	(240)
Proceeds from recoveries and reinsurance	99	85	131
Operating and employee related expenses paid	(136)	(130)	(238)
Interest paid, net of interest converted to principal	(139)	(169)	(179)
Income taxes (paid) received	(5)	(9)	(17)
Net cash provided (used) by operating activities	(142)	(55)	(333)
Cash flows from investing activities:
Purchases of available-for-sale investments	(2,661)	(2,146)	(1,494)
Sales of available-for-sale investments	2,412	1,145	757
Paydowns and maturities of available-for-sale investments	680	800	484
Purchases of investments at fair value	(199)	(390)	(631)
Sales, paydowns and maturities of investments at fair value	260	551	789
Sales, paydowns and maturities (purchases) of short-term investments, net	(125)	525	515
Sales, paydowns and maturities of held-to-maturity investments	1,799	67	44
Purchases of loans at fair value	0	0	(310)
Paydowns and maturities of loans receivable	261	232	313
Consolidation of variable interest entities	9	7	221
Deconsolidation of variable interest entities	(8)	0	18
(Payments) proceeds for derivative settlements	(44)	13	(26)
Collateral (to) from swap counterparty	49	(31)	144
Capital expenditures	(1)	(3)	(13)
Other investing	(8)	47	1
Net cash provided (used) by investing activities	2,424	817	812
Cash flows from financing activities:
Proceeds from investment agreements	19	24	30
Principal paydowns of investment agreements	(85)	(116)	(192)
Principal paydowns of medium-term notes	(129)	(118)	(168)
Principal paydowns of variable interest entity notes	(2,234)	(490)	(609)
Proceeds from issuance of variable interest entity notes	0	0	79
Principal paydowns of long-term debt	0	(11)	0
Purchases of treasury stock	(108)	(303)	(32)
Other financing	(5)	0	0
Net cash provided (used) by financing activities	(2,542)	(1,014)	(892)
Effect of exchange rate changes on cash and cash equivalents	(2)	(8)	(8)
Net increase (decrease) in cash and cash equivalents	(262)	(260)	(421)
Cash and cash equivalents - beginning of year	522	782	1,258
Reclassification to assets held for sale	(73)	0	(55)
Cash and cash equivalents - end of year	187	522	782
Reconciliation of net income (loss) to net cash provided (used) by operating activities: [Abstract]
Net income (loss)	(338)	180	569
Change in: [Abstract]
Premiums receivable	75	50	138
Deferred acquisition costs	41	49	43
Unearned premium revenue	(263)	(371)	(412)
Loss and loss adjustment expense reserves	29	12	(133)
Insurance loss recoverable	(74)	(44)	162
Accrued interest payable	111	105	106
Accrued expenses	7	14	(36)
Net investment losses related to other-than-temporary impairments	5	13	15
Realized (gains) losses and other settlements on insured derivatives	0	0	30
Unrealized (gains) losses on insured derivatives	(21)	(157)	(903)
Net (gains) losses on financial instruments at fair value and foreign exchange	(84)	(105)	(128)
Other net realized (gains) losses	282	(17)	(25)
Deferred income tax provision (benefit)	(5)	107	50
Share-based compensation	0	0	0
Interest on variable interest entities, net	57	71	77
Other operating	36	38	114
Total adjustments to net income (loss)	196	(235)	(902)
Net cash provided (used) by operating activities	$ (142)	$ (55)	$ (333)