Contracts Accounted for as Credit Derivatives - Net Change in Fair Value of Credit Derivatives Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Credit Derivatives
Realized gains on credit derivatives	$ 2	$ 6	$ 4	$ 11
Net credit derivative losses (paid and payable) recovered and recoverable and other settlements	(1)	(1)	(1)	9
Realized gains (losses) and other settlements	1	5	3	20
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	47	(11)	79	28
Net change in fair value of credit derivatives	48	(6)	82	48
Pooled Infrastructure Transactions [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	2	(1)	3	5
Collateralized Debt Obligations [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	34	(14)	31	6
Infrastructure Finance [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	7	1	17	2
Other [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	3	(1)	1	2
United States [Member] | RMBS [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	$ 1	$ 4	$ 27	$ 13