Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	$ 553,421	$ 548,185	$ 538,257	$ 515,630	$ 501,718	$ 489,871	$ 538,257	$ 489,871
Other comprehensive income (loss) - before reclassifications	(198)			1,790			8,432	10,499
Amount reclassified from accumulated other comprehensive income	(201)			(87)			(1,356)	(261)
Other comprehensive (loss) income, net of tax	(399)	544	6,931	1,703	5,237	3,298	7,076	10,238
Balance	560,528	553,421	548,185	526,163	515,630	501,718	560,528	526,163
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	11,936	11,392	4,461	(1,774)	(7,011)	(10,309)	4,461	(10,309)
Other comprehensive (loss) income, net of tax	(399)	544	6,931	1,703	5,237	3,298
Balance	11,537	11,936	11,392	(71)	(1,774)	(7,011)	11,537	(71)
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	8,061		286	(1,707)		(10,416)	286	(10,416)
Other comprehensive income (loss) - before reclassifications	(198)			1,790			8,432	10,499
Amount reclassified from accumulated other comprehensive income	0			0			(855)	0
Other comprehensive (loss) income, net of tax	(198)			1,790			7,577	10,499
Balance	7,863	8,061		83	(1,707)		7,863	83
Net Change in Overfunded Position in Pension and Postretirement Plans Arising During the Year, Net of Tax [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	4,840		4,840	423		423	4,840	423
Other comprehensive income (loss) - before reclassifications	0			0			0	0
Amount reclassified from accumulated other comprehensive income	0			0			0	0
Other comprehensive (loss) income, net of tax	0			0			0	0
Balance	4,840	4,840		423	423		4,840	423
Net Change in Net Actuarial Gain and Prior Service Credit on Pension and Postretirement Benefit Plans, Net of Tax [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	(965)		$ (665)	(490)		$ (316)	(665)	(316)
Other comprehensive income (loss) - before reclassifications	0			0			0	0
Amount reclassified from accumulated other comprehensive income	(201)			(87)			(501)	(261)
Other comprehensive (loss) income, net of tax	(201)			(87)			(501)	(261)
Balance	$ (1,166)	$ (965)		$ (577)	$ (490)		$ (1,166)	$ (577)