Contracts Accounted for as Credit Derivatives - Net Change in Fair Value of Credit Derivatives Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Credit Derivatives
Realized gains on credit derivatives	$ 2	$ 4	$ 6	$ 15
Net credit derivative losses (paid and payable) recovered and recoverable and other settlements	(1)	(5)	(2)	4
Realized gains (losses) and other settlements	1	(1)	4	19
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	20	59	99	87
Net change in fair value of credit derivatives	21	58	103	106
Pooled Infrastructure Transactions [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	4	(1)	7	4
Collateralized Debt Obligations [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	7	35	38	41
Infrastructure Finance [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	10	0	27	2
Other [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	1	14	2	16
United States [Member] | RMBS [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	$ (2)	$ 11	$ 25	$ 24