Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Statement of Cash Flows [Abstract]
Net cash flows provided by (used in) operating activities	$ (198)	$ 444
Fixed-maturity securities:
Purchases	(503)	(879)
Sales	914	592
Maturities and paydowns	506	533
Short-term investments with original maturities of over three months:
Purchases	(209)	(121)
Sales	2	1
Maturities and paydowns	174	104
Net sales (purchases) of short-term investments with original maturities of less than three months	(389)	(288)
Net proceeds from paydowns on financial guaranty variable interest entities’ assets	50	60
Net proceeds from sales of financial guaranty variable interest entities’ assets	51	0
Other	35	(16)
Net cash flows provided by (used in) investing activities	631	(14)
Financing activities
Dividends paid	(39)	(37)
Repurchases of common stock	(190)	(250)
Repurchases of common stock to pay withholding taxes	(16)	(13)
Net paydowns of financial guaranty variable interest entities’ liabilities	(95)	(61)
Paydown of long-term debt	(4)	(24)
Proceeds from option exercises	1	1
Net cash flows provided by (used in) financing activities	(343)	(384)
Effect of foreign exchange rate changes	0	(1)
Increase (decrease) in cash and restricted cash	90	45
Cash and restricted cash at beginning of period (see Note 7)	104	144
Cash and restricted cash at end of period (see Note 7)	194	189
Supplemental cash flow information
Income taxes	(3)	39
Interest on long-term debt	$ 42	$ 57