Contracts Accounted for as Credit Derivatives - Credit Derivatives Subordination and Ratings (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	$ 5,615	$ 6,207
Credit Risk Derivatives, at Fair Value, Net	(236)	(269)
Expected loss to be recovered	6	14
Collateralized Debt Obligations [Member] | TruPS CDOs [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	767	878
Credit Risk Derivatives, at Fair Value, Net	(75)	(72)
RMBS [Member] | United States [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	886	916
Credit Risk Derivatives, at Fair Value, Net	(28)	(53)
Pooled Infrastructure Transactions [Member] | United States [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,577	1,561
Credit Risk Derivatives, at Fair Value, Net	(41)	(42)
Infrastructure Finance [Member] | United States [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	544	572
Credit Risk Derivatives, at Fair Value, Net	(26)	(36)
Other [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,841	2,280
Credit Risk Derivatives, at Fair Value, Net	$ (66)	$ (66)