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	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Allowance For Loan And Lease Losses [Abstract]
Beginning balance	$ 240	$ 188
Net change in allowance for unfunded loan commitments and letters of credit	(1)	29
Ending balance	$ 239	$ 217