Accumulated Other Comprehensive Income - Amount reclassified from accumulated other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains (losses), net		$ 5	$ 5	$ 111
Change in funded status of post retirement benefits, net of taxes	$ 315	471	944	1,415
Income tax expense	(4,639)	(4,063)	(14,172)	(11,447)
Net Income	18,051	16,098	54,588	45,589
Amount reclassified from accumulated other comprehensive income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net Income	(315)	(467)	(940)	(1,332)
Unrealized gain (loss) on securities available-for-sale | Amount reclassified from accumulated other comprehensive income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Securities gains (losses), net		5	5	111
Income tax expense		(1)	(1)	(28)
Net Income		4	4	83
Retirement plans | Amount reclassified from accumulated other comprehensive income
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Change in funded status of post retirement benefits, net of taxes	(420)	(518)	(1,260)	(1,554)
Income tax expense	105	47	316	139
Net Income	$ (315)	$ (471)	$ (944)	$ (1,415)