Consolidated Variable Interest Entities - Effect of Consolidating FG VIE's on Financial Information (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Variable Interest Entity [Line Items]
Net earned premiums	[1]	$ 213	$ 144	$ 574	$ 412
Net investment income		112	102	311	301
Net realized investment gains (losses)		(27)	(19)	(20)	(25)
Fair value gains (losses) on FG VIEs		2	50	0	232
Other income (loss)		(3)	(11)	43	17
Loss and LAE		112	(44)	318	54
Income (loss) before income taxes		172	488	847	775
Provision (benefit) for income taxes		43	133	220	219
Net income (loss)		129	355	627	556
Net cash flows provided by (used in) operating activities				(39)	347
Effect on shareholders’ equity (decrease) increase		5,819		5,819		$ 5,758
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Net earned premiums		(6)	(5)	(16)	(27)
Net investment income		(3)	(2)	(9)	(8)
Net realized investment gains (losses)		6	0	9	(5)
Fair value gains (losses) on FG VIEs		2	50	0	232
Bargain purchase gain and settlement of pre-existing relationships resulting from Radian Asset Acquisition, after-tax		0	0	2	0
Other income (loss)		0	0	0	(2)
Loss and LAE		11	14	18	21
Income (loss) before income taxes		10	57	4	211
Provision (benefit) for income taxes		4	20	1	74
Net income (loss)		6	37	3	137
Net cash flows provided by (used in) operating activities		11	$ 18	44	$ 57
Effect on shareholders’ equity (decrease) increase		$ (38)		$ (38)		$ (44)

[1] Excludes $6 million and $5 million for Third Quarter 2015 and 2014, respectively, and $16 million and $27 million for Nine Months 2015 and 2014, respectively, related to consolidated financial guaranty ("FG") VIEs.