Contracts Accounted for as Credit Derivatives - Credit Derivatives Subordination and Ratings (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	$ 6,475	$ 6,207
Credit risk derivatives, at fair value, net	(237)	(269)
Expected loss to be recovered	4	14
Collateralized Debt Obligations [Member] | TruPS CDOs [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	702	878
Credit risk derivatives, at fair value, net	(32)	(72)
RMBS [Member] | United States [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	765	916
Credit risk derivatives, at fair value, net	(30)	(53)
Pooled Infrastructure Transactions [Member] | United States [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,408	1,561
Credit risk derivatives, at fair value, net	(35)	(42)
Infrastructure Finance [Member] | United States [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,306	572
Credit risk derivatives, at fair value, net	(71)	(36)
Other [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	2,294	2,280
Credit risk derivatives, at fair value, net	$ (69)	$ (66)