CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 159,139	$ 96,070	$ 81,051
Other comprehensive income (loss) net of tax:
Unrealized holding gain (loss) on securities available for sale arising during the period, net of tax of $3,174, $5,193, and $4,893	(13,872)	9,645	(9,087)
Unrealized gain (loss) on cash flow hedges arising during the period, net of tax of $52, $4, and $128	437	9	(240)
Reclassification adjustment for net gains included in net income, net of tax of $797, $576, and $749	(3,002)	(1,070)	(1,390)
Defined benefit pension plans, net of tax of $1,001, $1,125, and $809
Net gain (loss) arising during period	(1,435)	2,686	(470)
Amortization of prior service cost	(16)	(597)	(1,032)
Period change	(17,888)	10,673	(12,219)
Comprehensive income	$ 141,251	$ 106,743	$ 68,832