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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Total Revenue [Member]
Realized and Unrealized Gains and Losses [Line Items]
Total Realized and Unrealized Gains (Losses) Recorded in Revenue	$ 20	$ 28	$ 73	$ 57
Change in Unrealized Gains (Losses) Related to Financial Instruments Held	(1)	5	2	3
Trading services
Realized and Unrealized Gains and Losses [Line Items]
Total Realized and Unrealized Gains (Losses) Recorded in Revenue	(1)	8	25	4
Change in Unrealized Gains (Losses) Related to Financial Instruments Held	(1)	5	2	3
Total Fee Revenue [Member]
Realized and Unrealized Gains and Losses [Line Items]
Total Realized and Unrealized Gains (Losses) Recorded in Revenue	(1)	8	25	4
Change in Unrealized Gains (Losses) Related to Financial Instruments Held	(1)	5	2	3
Interest Income [Member]
Realized and Unrealized Gains and Losses [Line Items]
Total Realized and Unrealized Gains (Losses) Recorded in Revenue	21	20	48	53
Change in Unrealized Gains (Losses) Related to Financial Instruments Held	$ 0	$ 0	$ 0	$ 0