Contracts Accounted for as Credit Derivatives - Credit Derivatives Subordination and Ratings (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	$ 6,120	$ 6,182
Credit risk derivatives, at fair value, net	(228)	(207)
Expected loss to be recovered	6	2
Collateralized Debt Obligations [Member] | TruPS CDOs [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	606	642
Credit risk derivatives, at fair value, net	(22)	(28)
RMBS [Member] | United States [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	588	641
Credit risk derivatives, at fair value, net	(30)	(31)
Pooled Infrastructure Transactions [Member] | United States [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,403	1,373
Credit risk derivatives, at fair value, net	(41)	(34)
Regulated Utilities [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,115	1,096
Credit risk derivatives, at fair value, net	(10)	(11)
Infrastructure Finance [Member] | United States [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,294	1,300
Credit risk derivatives, at fair value, net	(87)	(63)
Other [Member]
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,114	1,130
Credit risk derivatives, at fair value, net	$ (38)	$ (40)