Derivatives (Effects of Derivative Instruments on the Statements of Income) (Details) - Interest Rate Swaps Designated as Hedges [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	$ 3,140	$ (638)	$ 2,424	$ 262
Other Noninterest Income [Member] | All Other Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	4,324	1,363	8,733	4,474
Cash Flow Hedge [Member] | Interest Income [Member] | Variable Rate Loans [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	(956)	(1,276)	(4,632)	(2,841)
Fair Value Hedging [Member] | Interest Income [Member] | Securities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	15		15
Fair Value Hedging [Member] | Interest Expense [Member] | Brokered Deposits [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	$ (243)	$ (725)	$ (1,692)	$ (1,371)