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	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance For Loan And Lease Losses [Abstract]
Beginning balance	$ 259	$ 242	$ 250
Net change in allowance for unfunded loan commitments and letters of credit	2	17	(8)
Ending balance	$ 261	$ 259	$ 242