Derivatives (Effects of Derivative Instruments on the Statements of Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	$ 1,479	$ 123	$ (716)	$ 900
Other Noninterest Income [Member] | All Other Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	3,600	1,588	4,409	3,111
Cash Flow Hedge [Member] | Interest Income [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	(1,660)	(946)	(3,676)	(1,565)
Fair Value Hedging [Member] | Interest Expense [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative income reflected in income statement	$ (461)	$ (519)	$ (1,449)	$ (646)