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, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Total Revenue [Member]
Realized and Unrealized Gains and Losses [Line Items]
Total Realized and Unrealized Gains (Losses) Recorded in Revenue	$ 7	$ 14	$ 52	$ 32
Change in Unrealized Gains (Losses) Related to Financial Instruments Held	(4)	(1)	11	(2)
Trading services
Realized and Unrealized Gains and Losses [Line Items]
Total Realized and Unrealized Gains (Losses) Recorded in Revenue	(6)	(1)	26	(1)
Change in Unrealized Gains (Losses) Related to Financial Instruments Held	(4)	(1)	11	(2)
Total Fee Revenue [Member]
Realized and Unrealized Gains and Losses [Line Items]
Total Realized and Unrealized Gains (Losses) Recorded in Revenue	(6)	(1)	26	(1)
Change in Unrealized Gains (Losses) Related to Financial Instruments Held	(4)	(1)	11	(2)
Interest Income [Member]
Realized and Unrealized Gains and Losses [Line Items]
Total Realized and Unrealized Gains (Losses) Recorded in Revenue	13	15	26	33
Change in Unrealized Gains (Losses) Related to Financial Instruments Held	$ 0	$ 0	$ 0	$ 0