Revenue from Contracts with Customers Revenue from Contracts with Customers (Schedule of Contract with Customer, Asset and Liability) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Bank Card Transaction Fees [Member]
Contract with Customer, Asset and Liability [Line Items]
Contract with Customer, Receivable	$ 10,978	$ 13,315	$ 10,810	$ 14,686
Trust Fees [Member]
Contract with Customer, Asset and Liability [Line Items]
Contract with Customer, Receivable	3,116	2,802	2,627	2,681
Deposit Account Charges and Other Fees [Member]
Contract with Customer, Asset and Liability [Line Items]
Contract with Customer, Receivable	4,682	5,597	4,467	5,735
Consumer Brokerage Services [Member]
Contract with Customer, Asset and Liability [Line Items]
Contract with Customer, Receivable	$ 690	$ 380	$ 353	$ 309