Fair Value (Level 3 Total Realized And Unrealized Gains And Losses Recorded In Revenue) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2011
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	$ 1	$ (18)	$ 7	$ (20)
Fair Value, Assets and Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Trading Revenue		(27)	(5)	(16)
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	1	(18)	7	(20)
Fair Value, Assets and Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Trading Revenue		(27)	(5)	(16)
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	80	210	226	354
Fair Value, Assets and Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Trading Revenue		0	0	0
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	81	192	233	334
Fair Value, Assets and Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Trading Revenue	$ 0	$ (27)	$ (5)	$ (16)