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, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Other Comprehensive Income	$ 9	$ 7	$ 14
Amount of Gain (Loss) Reclassified from OCI to Consolidated Statement of Income	(7)	(7)
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	3	5
Net Interest Revenue [Member]
Derivative [Line Items]
Amount of Gain (Loss) Reclassified from OCI to Consolidated Statement of Income	(7)	(7)
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	3	5
Interest-Rate Contracts [Member]
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Other Comprehensive Income	$ 9	$ 7	$ 14