Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	$ 568,161	$ 538,257
Other comprehensive income (loss) - before reclassifications	(4,461)	7,945
Amount reclassified from accumulated other comprehensive income	(207)	(1,014)
Other comprehensive income (loss), net of tax	(4,668)	6,931
Balance	571,031	548,185
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance	11,936	4,461
Other comprehensive income (loss), net of tax	(4,668)	6,931
Balance	7,268	11,392
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	7,186	286
Other comprehensive income (loss) - before reclassifications	(4,461)	7,945
Amount reclassified from accumulated other comprehensive income	0	(855)
Other comprehensive income (loss), net of tax	(4,461)	7,090
Balance	2,725	7,376
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	6,084	4,840
Other comprehensive income (loss) - before reclassifications	0	0
Amount reclassified from accumulated other comprehensive income	0	0
Other comprehensive income (loss), net of tax	0	0
Balance	6,084	4,840
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	(1,334)	(665)
Other comprehensive income (loss) - before reclassifications	0	0
Amount reclassified from accumulated other comprehensive income	(207)	(159)
Other comprehensive income (loss), net of tax	(207)	(159)
Balance	$ (1,541)	$ (824)