Derivative and Credit-Related Financial Instruments (Summary of Internally Classified Watch List Letters of Credit) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2011	Dec. 31, 2010
Derivative and Credit-Related Financial Instruments
Total watch list standby and commercial letters of credit	$ 233	$ 243
As a percentage of total outstanding standby and commercial letters of credit	4.30%	4.40%

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