Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 38,332	$ 48,862	$ 39,526
Other comprehensive income (loss), net of tax:
Securities available for sale and transferred securities	13,870	9,323	(4,494)
Hedging derivative instruments	202	(242)	(276)
Pension and post-retirement obligations	2,569	470	(4,595)
Total other comprehensive income (loss), net of tax	16,641	9,551	(9,365)
Comprehensive income	$ 54,973	$ 58,413	$ 30,161