Comprehensive Income (Loss), Net of Tax - Reclassification Out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Provision for Income Taxes	$ (11,036)	$ (9,600)	$ (9,026)
NET INCOME	40,827	37,475	36,279
Salaries and Employee Benefits	42,061	38,402	38,788
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
NET INCOME	(354)	(677)	(322)
Unrealized Gains and Losses on Available for Sale Securities | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss on Securities Transactions, Net	(37)	0	0
Total before tax	(37)	0	0
Provision for Income Taxes	9	0	0
NET INCOME	(28)	0	0
Net Prior Service (Cost) Credit | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Employee Benefits	(211)	(224)	(108)
Net Actuarial Gain (Loss) | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Employee Benefits	(227)	(684)	(325)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	(438)	(908)	(433)
Provision for Income Taxes	112	231	111
NET INCOME	$ (326)	$ (677)	$ (322)