Variable Interest Entities - Consolidated FG VIE's By Type of Collateral (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	$ 467	$ 570
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	517	627
Financial guaranty variable interest entities' assets without recourse, at fair value	102	130
Financial guaranty variable interest entities’ liabilities without recourse, at fair value	102	130
Financial guaranty variable interest entities’ assets, at fair value	569	700
Financial guaranty variable interest entities’ liabilities, at fair value	619	757
Manufactured Housing Loans [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	53	64
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	54	65
United States [Member] | First Lien [Member] | Residential Mortgage-Backed Securities (RMBS) [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	299	362
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	326	385
United States [Member] | Second Lien [Member] | Residential Mortgage-Backed Securities (RMBS) [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	115	144
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	$ 137	$ 177