Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 14,369	$ 11,741
Available-for-sale investment securities:
Gross unrealized holding gain (loss) arising during the period	8,725	(10,113)
Related tax (expense) benefit	(1,832)	3,178
Less: reclassification adjustment for net gain included in net income	30	1
Related tax expense	(6)	0
Amounts reclassified out of accumulated other comprehensive loss per ASU 2016-01 (a)	0	(5,020)
Net effect on other comprehensive income (loss)	6,869	(11,956)
Defined benefit plans:
Net gain arising during the period	2	0
Amortization of unrecognized loss and service cost on benefit plans	17	26
Related tax expense	(4)	(6)
Net effect on other comprehensive income	15	20
Cash flow hedges:
Net (loss) gain arising during the period	(1,833)	1,378
Related tax benefit (expense)	385	(289)
Net effect on other comprehensive (loss) income	(1,448)	1,089
Total other comprehensive income (loss), net of tax	5,436	(10,847)
Total comprehensive income	$ 19,805	$ 894