Loans And Allowance For Loan Losses (Narrative) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Loans And Allowance For Loan Losses [Abstract]
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 to the Federal Reserve Bank as collateral for discount window borrowings	1,700,000,000
Troubled Debt Restructured Loans	73,100,000
Accruing Restructured Loans	65,900,000	$ 50,249,000
Restructured Loans NonAccrual	7,200,000
Restructured commercial loans performing under their modified terms	51,000,000
Aggregate restructured credit card loans held	7,000,000
Restructured Loans Due to Bankruptcy Proceeding	$ 7,700,000
Period after which loans are deemed in default (in days)	90 days
Effect on Interest Income Resulting From Modification to Credit Card Loans	$ (979,000)
Commitments to lend additional funds to customers with restructured loans	10,600,000
Fair Value of Personal Real Estate Loans Held for Sale	11,300,000
Unpaid Principal Balance on Personal Real Estate Loans Held for Sale	10,900,000
Student Loans Held for Sale, Lower of Cost or Fair Value	6,000,000
Non-accrual HFS loans	0
Loans HFS 90 Days Past Due and Still Accruing	0
Foreclosed real estate	1,100,000	366,000
Personal property acquired in repossession	$ 2,700,000	$ 2,200,000