Consolidated Statements of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Statement of Cash Flows [Abstract]
Net cash flows provided by (used in) operating activities	$ (39)	$ 347
Fixed-maturity securities:
Purchases	(1,844)	(2,031)
Sales	1,719	951
Maturities	635	557
Net sales (purchases) of short-term investments	751	89
Net proceeds from paydowns on financial guaranty variable interest entities’ assets	114	346
Acquisition of Radian Asset, net of cash acquired	(800)	0
Other	59	9
Net cash flows provided by (used in) investing activities	634	(79)
Financing activities
Dividends paid	(55)	(58)
Repurchases of common stock	(420)	(438)
Share activity under option and incentive plans	(2)	(1)
Net paydowns of financial guaranty variable interest entities’ liabilities	(122)	(348)
Proceeds from issuance of long-term debt	0	495
Repayment of long-term debt	(3)	(18)
Net cash flows provided by (used in) financing activities	(602)	(368)
Effect of foreign exchange rate changes	(2)	(2)
Increase (decrease) in cash	(9)	(102)
Cash at beginning of period	75	184
Cash at end of period	66	82
Supplemental cash flow information
Income taxes	71	68
Interest	$ 55	$ 45