Derivative Financial Instruments (Derivatives not Designated as Hedging Instruments, Effect in Statements of Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Interest Rate Commitments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	$ 32	$ 641	$ 639	$ 2,387
Commitments to sell mortgage loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	59	(665)	(1,321)	(2,845)
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	1,543	1,154	2,062	1,873
Not Designated as Hedging Instrument [Member] | Interest Rate Commitments [Member] | Mortgage banking revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	32	641	639	2,387
Not Designated as Hedging Instrument [Member] | Commitments to sell mortgage loans [Member] | Mortgage banking revenues [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	59	(665)	(1,321)	(2,845)
Not Designated as Hedging Instrument [Member] | Interest rate swaps with customers [Member] | Loan related derivative income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	1,917	32	5,583	17,064
Not Designated as Hedging Instrument [Member] | Mirror swaps with counterparties [Member] | Loan related derivative income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	(505)	1,250	(2,578)	(14,527)
Not Designated as Hedging Instrument [Member] | Risk participation agreements [Member] | Loan related derivative income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income	$ 40	$ (104)	$ (261)	$ (206)