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	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Allowance For Loan And Lease Losses [Abstract]
Beginning balance	$ 261	$ 259
Net change in allowance for unfunded loan commitments and letters of credit	21	(25)
Ending balance	$ 282	$ 234