Fair Value - Level 3 Total Realized And Unrealized Gains And Losses Recorded In Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Total revenue
Realized and Unrealized Gains and Losses [Line Items]
Total realized and unrealized gains (losses) recorded in revenue	$ 13	$ 20	$ 28	$ 73
Change in unrealized gains (losses) related to financial instruments held	0	(1)	0	2
Trading services
Realized and Unrealized Gains and Losses [Line Items]
Total realized and unrealized gains (losses) recorded in revenue	0	(1)	(2)	25
Change in unrealized gains (losses) related to financial instruments held	0	(1)	0	2
Total fee revenue
Realized and Unrealized Gains and Losses [Line Items]
Total realized and unrealized gains (losses) recorded in revenue	0	(1)	(2)	25
Change in unrealized gains (losses) related to financial instruments held	0	(1)	0	2
Net interest revenue
Realized and Unrealized Gains and Losses [Line Items]
Total realized and unrealized gains (losses) recorded in revenue	13	21	30	48
Change in unrealized gains (losses) related to financial instruments held	$ 0	$ 0	$ 0	$ 0