Contracts Accounted for as Credit Derivatives - Net Change in Fair Value of Credit Derivatives Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Credit Derivatives
Realized gains on credit derivatives	$ 2	$ 5
Net credit derivative losses (paid and payable) recovered and recoverable and other settlements	0	10
Realized gains (losses) and other settlements	2	15
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	32	39
Net change in fair value of credit derivatives	34	54
Pooled Infrastructure Transactions [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	1	6
Collateralized Debt Obligations [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	(3)	20
Infrastructure Finance [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	10	1
Other [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	(2)	3
United States [Member] | RMBS [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	$ 26	$ 9