Derivative Financial Instruments (Schedule of Differences Between the Gains (Losses) on the Derivative and The Gains (Losses) on the Hedged Item) (Details) (Derivatives designed as cash flow value hedges, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Other Comprehensive Income	$ (56)	$ (2)	$ 108	$ 2
Amount of Gain (Loss) Reclassified from OCI to Consolidated Statement of Income	(1)	(1)	(3)	(4)
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	1	3	8	4
Interest-rate contracts
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Other Comprehensive Income	(1)	0	10	3
Interest-rate contracts | Net interest revenue
Derivative [Line Items]
Amount of Gain (Loss) Reclassified from OCI to Consolidated Statement of Income	(1)	(1)	(3)	(4)
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	1	1	3	2
Foreign exchange contracts
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Other Comprehensive Income	(55)	(2)	98	(1)
Foreign exchange contracts | Net interest revenue
Derivative [Line Items]
Amount of Gain (Loss) Reclassified from OCI to Consolidated Statement of Income	0	0	0	0
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	$ 0	$ 2	$ 5	$ 2