Derivative Financial Instruments (Schedule of Differences Between the Gains (Losses) on the Derivative and the Gains (Losses) on the Hedged Item) (Details) (Derivatives Designated as Cash Flow Value Hedges [Member], USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Amount of Gain (Loss) on Derivative Recognized in Other Comprehensive Income	$ 4	$ 5	$ 4	$ 5
Amount of Gain (Loss) Reclassified from OCI to Consolidated Statement of Income	(2)	(2)	(4)	(3)
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	1		2	2
Interest-Rate Contracts [Member]
Amount of Gain (Loss) on Derivative Recognized in Other Comprehensive Income	4	5	4	5
Net Interest Revenue [Member]
Amount of Gain (Loss) Reclassified from OCI to Consolidated Statement of Income	(2)	(2)	(4)	(3)
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	$ 1		$ 2	$ 2