Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Statement of Cash Flows [Abstract]
Net cash flows provided by (used in) operating activities	$ (47)	$ 105
Fixed-maturity securities:
Purchases	(510)	(1,172)
Sales	739	1,381
Maturities	645	411
Net sales (purchases) of short-term investments	(190)	382
Net proceeds from paydowns on financial guaranty variable interest entities’ assets	556	70
Acquisition of Radian Asset, net of cash acquired	0	(800)
Cash restricted for CIFG acquisition	(451)	0
Other	(12)	27
Net cash flows provided by (used in) investing activities	777	299
Financing activities
Dividends paid	(35)	(37)
Repurchases of common stock	(135)	(285)
Share activity under option and incentive plans	(1)	(2)
Net paydowns of financial guaranty variable interest entities’ liabilities	(531)	(78)
Repayment of long-term debt	(1)	(2)
Net cash flows provided by (used in) financing activities	(703)	(404)
Effect of foreign exchange rate changes	(3)	0
Increase (decrease) in cash	24	0
Cash at beginning of period	166	75
Cash at end of period	190	75
Supplemental cash flow information
Income taxes	1	51
Interest	$ 48	$ 48