CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 25,252	$ 28,525	$ 64,141	$ 77,840
Change in available-for-sale and transferred securities:
Unrealized holding gain (loss) on securities available-for-sale arising during the period	(64,432)	(80,532)	(51,150)	(302,137)
Reclassification adjust for amortization of unrealized losses on securities transferred to held-to-maturity	501	504	1,486	995
Reclassification adjustment for losses included in net income	35	0	16	0
Net securities gain (loss) activity during the period	(63,896)	(80,028)	(49,648)	(301,142)
Tax effect	13,419	16,806	10,427	63,239
Net of tax amount	(50,477)	(63,222)	(39,221)	(237,903)
Defined benefit pension plans:
Amortization of net actuarial loss	15	36	45	108
Net gain activity during the period	15	36	45	108
Tax effect	(4)	(9)	(12)	(27)
Net of tax amount	11	27	33	81
Total other comprehensive income (loss), net of tax	(50,466)	(63,195)	(39,188)	(237,822)
Comprehensive income (loss)	$ (25,214)	$ (34,670)	$ 24,953	$ (159,982)