Contracts Accounted for as Credit Derivatives - Credit Derivatives Subordination and Ratings (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	$ 6,681	$ 6,207
Credit risk derivatives, at fair value, net	(257)	(269)
Expected loss to be recovered	5	14
Collateralized Debt Obligations [Member] | TruPS CDOs [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	750	878
Credit risk derivatives, at fair value, net	(40)	(72)
RMBS [Member] | United States [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	809	916
Credit risk derivatives, at fair value, net	(26)	(53)
Pooled Infrastructure Transactions [Member] | United States [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,427	1,561
Credit risk derivatives, at fair value, net	(39)	(42)
Infrastructure Finance [Member] | United States [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,322	572
Credit risk derivatives, at fair value, net	(81)	(36)
Other [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	2,373	2,280
Credit risk derivatives, at fair value, net	$ (71)	$ (66)