Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Statement of Cash Flows [Abstract]
Net cash flows provided by (used in) operating activities	$ 105	$ 222
Fixed-maturity securities:
Purchases	(1,172)	(1,357)
Sales	1,381	444
Maturities	411	397
Net sales (purchases) of short-term investments	382	(51)
Net proceeds from paydowns on financial guaranty variable interest entities’ assets	70	315
Acquisition of Radian Asset, net of cash acquired	(800)	0
Other	27	23
Net cash flows provided by (used in) investing activities	299	(229)
Financing activities
Dividends paid	(37)	(40)
Repurchases of common stock	(285)	(212)
Share activity under option and incentive plans	(2)	1
Net paydowns of financial guaranty variable interest entities’ liabilities	(78)	(311)
Proceeds from issuance of long-term debt	0	496
Repayment of long-term debt	(2)	(7)
Net cash flows provided by (used in) financing activities	(404)	(73)
Effect of foreign exchange rate changes	0	2
Increase (decrease) in cash	0	(78)
Cash at beginning of period	75	184
Cash at end of period	75	106
Supplemental cash flow information
Income taxes	51	68
Interest	$ 48	$ 36