CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 148,600	$ 164,460	$ 159,139
Other comprehensive income (loss) net of tax:
Unrealized holding gain (loss) on securities available for sale arising during the period, net of tax of $15,554, $12,946, and $3,174	58,513	48,703	(13,872)
Unrealized gain (loss) on cash flow hedges arising during the period, net of tax of $311, $226, and $52	(1,169)	(846)	437
Reclassification adjustment for net gains included in net income, net of tax of $2,308, $857, and $797	(8,681)	(3,224)	(3,002)
Defined benefit pension plans, net of tax of  $452, $1,239, and $1,001
Net gain (loss) arising during period	(1,767)	4,579	(1,435)
Amortization of prior service cost	66	84	(16)
Period change	46,962	49,296	(17,888)
Comprehensive income	$ 195,562	$ 213,756	$ 141,251