Variable Interest Entities - Consolidated FG VIE's By Type of Collateral (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	$ 364	$ 467
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	388	517
Financial guaranty variable interest entities' assets without recourse, at fair value	105	102
Financial guaranty variable interest entities’ liabilities without recourse, at fair value	105	102
Financial guaranty variable interest entities’ assets, at fair value	469	569
Financial guaranty variable interest entities’ liabilities, at fair value	493	619
Manufactured Housing Loans [Member]
Variable Interest Entity [Line Items]
Financial guaranty variable interest entities' assets with recourse, at fair value	0	53
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	0	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	289	299
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	314	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	75	115
Financial guaranty variable interest entities’ liabilities with recourse, at fair value	$ 74	$ 137