Accumulated Other Comprehensive Loss (Schedule of Changes In Each Component of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	$ 442,438	$ 419,272
Other comprehensive income before reclassifications	5,933	7,301
Amounts reclassified from other comprehensive loss	(2,698)	(2,215)
Other comprehensive income	3,235	5,086
Ending balance	$ 500,315	$ 434,784
Combined Federal and state income tax rate	37.00%	37.00%
Defined Benefit Pension Plans
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	$ (4,660)	$ (4,759)
Ending balance	(4,660)	(4,759)
Unrealized Gain (Losses) on Securities Available-for-Sale
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	(2,352)	927
Other comprehensive income before reclassifications	5,933	7,301
Amounts reclassified from other comprehensive loss	(2,698)	(2,215)
Other comprehensive income	3,235	5,086
Ending balance	883	6,013
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	(7,012)	(3,832)
Other comprehensive income	3,235	5,086
Ending balance	$ (3,777)	$ 1,254