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, 2017	Mar. 31, 2016
Credit Derivatives
Realized gains on credit derivatives	$ 5	$ 10
Net credit derivative losses (paid and payable) recovered and recoverable and other settlements	10	(2)
Realized gains (losses) and other settlements	15	8
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	39	(68)
Net change in fair value of credit derivatives	54	(60)
Pooled corporate obligations [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	20	(48)
Other [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	3	(5)
United States [Member] | RMBS [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	9	(15)
United States [Member] | Pooled Infrastructure Transactions [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	6	0
United States [Member] | Infrastructure Finance [Member]
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	1	0
Terminated And Settlement Of Credit Derivative Contracts [Member]
Credit Derivatives
Realized gains on credit derivatives	0	0
Net unrealized gains (losses):
Net change in unrealized gains (losses) on credit derivatives	15	11
Net par of terminated credit derivative contracts	184	0
Credit Derivative, Loss On Contract Termination	$ (12)	$ 0