Fair Value - Level 3 Total Realized And Unrealized Gains And Losses Recorded In Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Total revenue
Realized and Unrealized Gains and Losses [Line Items]
Total realized and unrealized gains (losses) recorded in revenue	$ 10	$ 7	$ 15	$ 52
Change in unrealized gains (losses) related to financial instruments held	0	(4)	0	11
Trading services
Realized and Unrealized Gains and Losses [Line Items]
Total realized and unrealized gains (losses) recorded in revenue	0	(6)	(2)	26
Change in unrealized gains (losses) related to financial instruments held	0	(4)	0	11
Total fee revenue
Realized and Unrealized Gains and Losses [Line Items]
Total realized and unrealized gains (losses) recorded in revenue	0	(6)	(2)	26
Change in unrealized gains (losses) related to financial instruments held	0	(4)	0	11
Net interest revenue
Realized and Unrealized Gains and Losses [Line Items]
Total realized and unrealized gains (losses) recorded in revenue	10	13	17	26
Change in unrealized gains (losses) related to financial instruments held	$ 0	$ 0	$ 0	$ 0