Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 27,643	$ 23,297	$ 85,122	$ 57,829
Unrealized gains (losses) on securities available for sale:
Unrealized holding gains (losses) arising during the period, pretax	3,673	19	(16,236)	23,556
Tax (expense) benefit	(844)	(4)	3,731	(5,413)
Reclassification to realized (gains) losses	0	0	0	(8,024)
Tax expense	0	0	0	1,844
Postretirement Plans:
Amortization of unrecognized net actuarial loss	109	153	485	511
Tax expense (benefit)	5	(35)	(112)	(118)
Other comprehensive income (loss)	2,943	133	(12,132)	12,356
Comprehensive income	$ 30,586	$ 23,430	$ 72,990	$ 70,185