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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Credit Derivatives
Realized gains on credit derivatives	$ 4	$ 11	$ 15	$ 39
Net credit derivative losses (paid and payable) recovered and recoverable and other settlements	(5)	4	4	8
Realized gains (losses) and other settlements	(1)	15	19	47
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	59	6	87	(23)
Net change in fair value of credit derivatives	58	21	106	24
Collateralized Debt Obligations [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	35	3	41	(37)
Other [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	14	10	16	4
United States [Member] | RMBS [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	11	(12)	24	0
United States [Member] | Pooled Infrastructure Transactions [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	(1)	4	4	10
United States [Member] | Infrastructure Finance [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	0	1	2	0
Terminated And Settlement Of Credit Derivative Contracts [Member]
Credit Derivatives
Realized gains on credit derivatives	0	3	0	11
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	8	11	24	81
Net par of terminated credit derivative contracts	40	1,071	273	3,507
Net credit derivative losses (paid and payable) recovered and recoverable and other settlements	$ (3)	$ 0	$ (15)	$ 0