Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 95,644	$ 81,477	$ 92,046
Unrealized (losses) gains on securities available for sale:
Unrealized holding (losses) gains arising during the period, pretax	(53,752)	18,729	22,230
Tax benefit (expense)	12,352	(4,304)	(5,157)
Reclassification to realized losses (gains)	1,237	(8,024)	(97)
Tax (benefit) expense	(284)	1,844	22
Postretirement plans:
Net gain (loss) arising during period	872	589	(686)
Tax (expense) benefit	(201)	(135)	158
Amortization of unrecognized net actuarial loss	592	686	814
Tax benefit	(136)	(158)	(200)
Other comprehensive (loss) income	(39,320)	9,227	17,084
Comprehensive income	$ 56,324	$ 90,704	$ 109,130