Variable Interest Entities - Consolidated FG VIE's By Type of Collateral (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	$ 456	$ 467
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	505	517
Financial guaranty variable interest entities' assets without recourse, at fair value	104	102
Financial guaranty variable interest entities’ liabilities without recourse, at fair value	104	102
Financial guaranty variable interest entities’ assets, at fair value	560	569
Financial guaranty variable interest entities’ liabilities, at fair value	609	619
Manufactured Housing Loans [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	50	53
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	52	54
United States [Member] | First Lien [Member] | RMBS [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	295	299
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	321	326
United States [Member] | Second Lien [Member] | RMBS [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	111	115
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	$ 132	$ 137