CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income	$ 84,337	$ 87,047	$ 80,411
Change in securities available-for-sale:
Unrealized holding gain (loss) on securities available-for-sale arising during the period	20,148	23,438	(7,339)
Reclassification adjustment for (gains) losses included in net income	(433)	(142)	50
Net securities gain (loss) activity during the period	19,715	23,296	(7,289)
Tax effect	(4,140)	(4,893)	1,637
Net of tax amount	15,575	18,403	(5,652)
Defined benefit pension plans:
Net gain (loss) on defined benefit pension plans	(105)	(409)	269
Amortization of net actuarial loss	251	205	266
Net gain (loss) on activity during the period	146	(204)	535
Tax effect	(36)	51	(163)
Net of tax amount	110	(153)	372
Total other comprehensive income (loss), net of tax	15,685	18,250	(5,280)
Comprehensive income	$ 100,022	$ 105,297	$ 75,131