Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance			$ 458,308	$ 432,686
Other comprehensive income (loss) - before reclassifications	$ (3,010)	$ 562	(9,556)	3,275
Amount reclassified from accumulated other comprehensive income	(194)	(29)	(1,638)	(84)
Other comprehensive (loss) income, net of tax	(3,204)	533	(9,848)	3,191
Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings, Tax Effect	(1,346)		(1,346)		$ (1,346)
Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings, Tax Effect			0
Balance	477,118	454,928	477,118	454,928
Accumulated Other Comprehensive (Loss) Income [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	(9,796)	(3,593)	(1,806)	(6,251)
Other comprehensive (loss) income, net of tax			(9,848)	3,191
Tax Cuts and Jobs Act of 2017, Reclassification from AOCI to Retained Earnings, Tax Effect			(1,346)
Balance	(13,000)	(3,060)	(13,000)	(3,060)
Net Unrealized Holding Gain (Loss) on Securities Available for Sale, Net of Tax [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	(11,576)	(4,049)	(5,030)	(6,762)
Other comprehensive income (loss) - before reclassifications	(3,010)	562	(9,556)	3,275
Amount reclassified from accumulated other comprehensive income	0	0	0	0
Other comprehensive (loss) income, net of tax	(3,010)	562	(9,556)	3,275
Balance	(14,586)	(3,487)	(14,586)	(3,487)
Net Change in Net Actuarial (Gain) loss and Prior Service Cost on Pension and Postretirement Benefit Plans, Net of Tax [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	3,126	456	3,224	511
Other comprehensive income (loss) - before reclassifications	0	0	0	0
Amount reclassified from accumulated other comprehensive income	(194)	(29)	(292)	(84)
Other comprehensive (loss) income, net of tax	(194)	(29)	(292)	(84)
Balance	$ 2,932	$ 427	$ 2,932	$ 427