Derivatives (Effects of Derivative Instruments on the Statement of Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative income reflected in income statement	$ (638)	$ 1,389	$ 262	$ 4,882
Interest Rate Swaps [Member] | Interest Income [Member] | Cash Flow Hedge [Member]
Derivative income reflected in income statement	(1,276)	(126)	(2,841)	(222)
Interest Rate Swaps [Member] | Interest Expense [Member] | Fair Value Hedging [Member]
Derivative income reflected in income statement	(725)	176	(1,371)	620
All Other Instruments [Member]
Derivative income reflected in income statement	$ 1,363	$ 1,339	$ 4,474	$ 4,484