Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Statement of Cash Flows [Abstract]
Net cash flows provided by (used in) operating activities	$ (190)	$ (39)
Fixed-maturity securities:
Purchases	(1,028)	(1,844)
Sales	877	1,719
Maturities	861	635
Net sales (purchases) of short-term investments	80	751
Net proceeds from paydowns on financial guaranty variable interest entities’ assets	590	114
Acquisition of Radian Asset, net of cash acquired	0	(800)
Acquisition of CIFG, net of cash acquired (see Note 2)	(435)	0
Other	(12)	59
Net cash flows provided by (used in) investing activities	933	634
Financing activities
Dividends paid	(52)	(55)
Repurchases of common stock	(190)	(420)
Share activity under option and incentive plans	4	(2)
Net paydowns of financial guaranty variable interest entities’ liabilities	(567)	(122)
Repayment of long-term debt	(2)	(3)
Net cash flows provided by (used in) financing activities	(807)	(602)
Effect of foreign exchange rate changes	(4)	(2)
Increase (decrease) in cash	(68)	(9)
Cash at beginning of period	166	75
Cash at end of period	98	66
Supplemental cash flow information
Income taxes	2	71
Interest	$ 55	$ 55