Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Cash Flows [Abstract]
Net cash flows provided by (used in) operating activities	$ 102	$ (90)
Fixed-maturity securities:
Purchases	(517)	(296)
Sales	323	162
Maturities	265	301
Net sales (purchases) of short-term investments	12	(63)
Net proceeds from paydowns on financial guaranty variable interest entities’ assets	46	66
Acquisition of MBIA UK, net of cash acquired (see Note 2)	95	0
Other	(13)	2
Net cash flows provided by (used in) investing activities	211	172
Financing activities
Dividends paid	(19)	(18)
Repurchases of common stock	(216)	(75)
Repurchases of common stock to pay withholding taxes	(12)	(2)
Net paydowns of financial guaranty variable interest entities’ liabilities	(48)	(42)
Repayment of long-term debt	(1)	0
Proceeds from options exercises	2	1
Net cash flows provided by (used in) financing activities	(294)	(136)
Effect of foreign exchange rate changes	2	0
Increase (decrease) in cash and restricted cash	21	(54)
Cash and restricted cash at beginning of period (see Note 10)	127	166
Cash and restricted cash at end of period (see Note 10)	148	112
Supplemental cash flow information
Income taxes	(5)	1
Interest	$ 8	$ 7