Loans And Allowance For Loan Losses (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Loans And Allowance For Loan Losses [Abstract]
Loans To Principal Holders (over 10% ownership in the Company's stock)	$ 0
Unfunded Loan Commitments	10,800,000,000
Unused Approved Credit Card Lines of Credit	5,100,000,000
Loans pledged at the Federal Home Loan Bank as collateral for borrowings and letters of credit obtained to secure public deposits	3,800,000,000
Loans pledged at the Federal Reserve Bank as collateral for discount window borrowings	1,700,000,000
Net Investment in Direct Financing and Sales Type Leases	737,700,000	$ 725,300,000
Capital Leases, Net Investment in Sales Type Leases, Deferred Income	52,100,000	49,900,000
Property Subject to or Available for Operating Lease, Net	17,400,000	19,000,000
Decrease in interest income resulting from modification to credit card loans	(1,000,000)
Commitments to lend additional funds to customers with restructured loans	7,600,000	10,300,000
Loans Held-for-sale, Fair Value Disclosure	15,300,000
Unpaid Principal Balance on Personal Real Estate Loans Held for Sale	14,800,000
Personal Real Estate Loans HFS Past Due	0
Personal Real Estate Loans HFS on Non-Accrual Status	0
Student Loans Held for Sale, Lower of Cost or Fair Value	6,100,000
HFS Student Loans on Non-Accrual Status	0
HFS Student Loans Past Due	0
Foreclosed real estate	681,000	366,000
Personal property acquired in repossession	$ 2,700,000	$ 2,200,000