Accumulated Other Comprehensive Income (Loss) - Schedule of Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive income (loss)	$ 14,350	$ 5,123
Unrealized Gain (Loss) on Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive income (loss)	20,448	9,743	$ (12,390)
Deferred tax asset (liability)	(4,699)	(2,239)	2,896
Total accumulated other comprehensive income (loss)	15,749	7,504	(9,494)
Postretirement Plans Asset (Liability)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive income (loss)	(1,817)	(3,092)	(3,220)
Deferred tax asset (liability)	418	711	753
Total accumulated other comprehensive income (loss)	(1,399)	(2,381)	(2,467)
Total
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total accumulated other comprehensive income (loss)	$ 14,350	$ 5,123	$ (11,961)