Allowances for Loan and Lease Losses and Unfunded Loan Commitments and Letters Of Credit (Rollforward of Allowance for Unfunded Loan Commitments and Letters of Credit) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Allowance For Loan And Lease Losses [Abstract]
Beginning balance	$ 250	$ 240
Net change in allowance for unfunded loan commitments and letters of credit	(8)	(16)
Ending balance	$ 242	$ 224