Consolidated Variable Interest Entities - Consolidated FG VIE's By Type of Collateral (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	$ 596	$ 725
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	657	807
Financial guaranty variable interest entities' assets without recourse, at fair value	111	151
Financial guaranty variable interest entities’ liabilities without recourse, at fair value	111	151
Financial guaranty variable interest entities’ assets, at fair value	707	876
Financial guaranty variable interest entities’ liabilities, at fair value	768	958
Manufactured Housing Loans [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	68	74
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	69	75
United States [Member] | First Lien [Member] | RMBS [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	378	473
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	400	509
United States [Member] | Second Lien [Member] | RMBS [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	150	178
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	$ 188	$ 223