CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 164,460	$ 159,139	$ 96,070
Other comprehensive income (loss) net of tax:
Unrealized holding gain (loss) on securities available for sale arising during the period, net of tax of $12,946, $3,174, and $5,193	48,703	(13,872)	9,645
Unrealized gain (loss) on cash flow hedges arising during the period, net of tax of $226, $52, and $4	(846)	437
Unrealized gain (loss) on cash flow hedges arising during the period, net of tax of $226, $52, and $4			9
Reclassification adjustment for net gains included in net income, net of tax of $857, $797, and $576	(3,224)	(3,002)	(1,070)
Defined benefit pension plans, net of tax of $1,239, $1,001, and $1,125
Net gain (loss) arising during period	4,579	(1,435)	2,686
Amortization of prior service cost	84	(16)	(597)
Period change	49,296	(17,888)	10,673
Comprehensive income	$ 213,756	$ 141,251	$ 106,743