Fair Value (Level 3 Total Realized And Unrealized Gains And Losses Recorded In Revenue) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Total Revenue [Member]
Realized and Unrealized Gains and Losses [Line Items]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Trading Revenue	$ 429	$ 548	$ 158
Fair Value, Assets and Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Trading Revenue	3	(9)	(5)
Trading services [Member]
Realized and Unrealized Gains and Losses [Line Items]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Trading Revenue	9	(13)	17
Fair Value, Assets and Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Trading Revenue	3	(9)	(5)
Total Fee Revenue [Member]
Realized and Unrealized Gains and Losses [Line Items]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Trading Revenue	9	(13)	17
Fair Value, Assets and Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Trading Revenue	3	(9)	(5)
Interest Income [Member]
Realized and Unrealized Gains and Losses [Line Items]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Trading Revenue	420	561	141
Fair Value, Assets and Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Trading Revenue	$ 0	$ 0	$ 0