Contracts Accounted for as Credit Derivatives - Credit Derivatives Subordination and Ratings (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	$ 5,658	$ 5,956
Net Fair Value Asset (Liability)	(159)	(185)
Expected loss to be recovered	13	4
Public finance | Non United States
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	2,409	2,676
Net Fair Value Asset (Liability)	(31)	(39)
Public finance | U.S.
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	2,075	1,942
Net Fair Value Asset (Liability)	(66)	(83)
Structured finance | Non United States
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	129	132
Net Fair Value Asset (Liability)	(4)	(5)
Structured finance | U.S.
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,045	1,206
Net Fair Value Asset (Liability)	$ (58)	$ (58)