Derivatives (Effects of Derivative Instruments on the Statement of Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative income reflected in income statement	$ 123	$ 2,773	$ 900	$ 3,493
Interest Rate Swaps [Member] | Interest Income [Member] | Cash Flow Hedge [Member]
Derivative income reflected in income statement	(946)	(210)	(1,565)	(96)
Interest Rate Swaps [Member] | Interest Expense [Member] | Fair Value Hedging [Member]
Derivative income reflected in income statement	(519)	303	(646)	444
All Other Instruments [Member]
Derivative income reflected in income statement	$ 1,588	$ 2,680	$ 3,111	$ 3,145