Derivative Financial Instruments (Derivatives not Designated as Hedging Instruments, Effect in Statements of Income) (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	$ 777	$ 783	$ 2,222	$ 519
Interest rate swaps with customers [Member] | Loan related derivative income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	(3,001)	3,921	(12,196)	3,666
Mirror swaps with counterparties [Member] | Loan related derivative income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	3,645	(2,551)	12,969	(2,073)
Risk participation agreements [Member] | Loan related derivative income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	0	(226)	0	(301)
Foreign exchange contracts [Member] | Loan related derivative income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	24	0	36	0
Interest rate lock commitments [Member] | Mortgage banking revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	191	(11)	177	607
Forward sale commitments [Member] | Mortgage banking revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	$ (82)	$ (350)	$ 1,236	$ (1,380)