Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Cash Flows [Abstract]
Net cash flows provided by (used in) operating activities	$ (90)	$ 23
Fixed-maturity securities:
Purchases	(296)	(448)
Sales	162	841
Maturities	301	155
Net sales (purchases) of short-term investments	(63)	420
Net proceeds from paydowns on financial guaranty variable interest entities’ assets	66	30
Other	2	3
Net cash flows provided by (used in) investing activities	172	1,001
Financing activities
Dividends paid	(18)	(19)
Repurchases of common stock	(75)	(152)
Share activity under option and incentive plans	0	(5)
Net paydowns of financial guaranty variable interest entities’ liabilities	(42)	(39)
Repayment of long-term debt	0	(1)
Other	(1)	4
Net cash flows provided by (used in) financing activities	(136)	(212)
Effect of foreign exchange rate changes	0	(2)
Increase (decrease) in cash	(54)	810
Cash at beginning of period	166	75
Cash at end of period	112	885
Supplemental cash flow information
Income taxes	1	17
Interest	$ 7	$ 7