Fair Value - Level 3 Total Realized And Unrealized Gains And Losses Recorded In Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Total revenue
Realized and Unrealized Gains and Losses [Line Items]
Total realized and unrealized gains (losses) recorded in revenue	$ 81	$ 85	$ 125
Change in unrealized gains (losses) related to financial instruments held	3	9	(1)
Trading services
Realized and Unrealized Gains and Losses [Line Items]
Total realized and unrealized gains (losses) recorded in revenue	25	11	63
Change in unrealized gains (losses) related to financial instruments held	3	9	(1)
Total fee revenue
Realized and Unrealized Gains and Losses [Line Items]
Total realized and unrealized gains (losses) recorded in revenue	25	11	63
Change in unrealized gains (losses) related to financial instruments held	3	9	(1)
Net interest revenue
Realized and Unrealized Gains and Losses [Line Items]
Total realized and unrealized gains (losses) recorded in revenue	56	74	62
Change in unrealized gains (losses) related to financial instruments held	$ 0	$ 0	$ 0