Consolidated Variable Interest Entities - Consolidated FG VIE's By Type of Collateral (Details) - USD ($) $ in Millions	Sep. 30, 2015		Dec. 31, 2014
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	$ 1,369	[1]	$ 1,239
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	1,315	[1]	1,277
Financial guaranty variable interest entities' assets without recourse, at fair value	178	[1]	163
Financial guaranty variable interest entities’ liabilities without recourse, at fair value	167	[1]	142
Financial guaranty variable interest entities’ assets, at fair value	1,547	[1]	1,402
Financial guaranty variable interest entities’ liabilities, at fair value	1,482	[1]	1,419
Other Insurance Product Line [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	448	[1]	369
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	448	[1]	369
United States [Member] | First Lien [Member] | RMBS [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	713	[1]	632
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	572	[1]	581
United States [Member] | Second Lien [Member] | RMBS [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	208	[1]	238
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	295	[1]	$ 327
Radian [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities’ assets, at fair value	115
Financial guaranty variable interest entities’ liabilities, at fair value	$ 111

[1] The September 30, 2015 amounts include $115 million of FG VIE assets and $111 million of FG VIE liabilities acquired from Radian Asset.