Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 10,210	$ 14,868	$ 14,194	$ 38,835
Available-for-sale investment securities:
Gross unrealized holding (loss) gain arising during the period	(2,974)	2,913	15,480	24,585
Related tax benefit (expense)	624	(612)	(3,251)	(5,163)
Reclassification adjustment for net gain included in net income	(2)	(97)	(383)	(70)
Related tax expense	0	21	80	15
Net effect on other comprehensive (loss) income	(2,352)	2,225	11,926	19,367
Defined benefit plans:
Net (loss) gain arising during the period	(533)	2	(1,054)	4
Related tax benefit (expense)	113	(1)	222	(1)
Amortization of unrecognized loss and service cost on benefit plans	33	17	97	54
Related tax expense	(7)	(3)	(21)	(11)
Recognition of loss due to settlement and curtailment	531	0	1,050	0
Related tax expense	(112)	0	(221)	0
Net effect on other comprehensive income	25	15	73	46
Cash flow hedges:
Net gain (loss) arising during the period	803	(1,857)	(9,661)	(6,824)
Related tax (expense) benefit	(168)	390	2,029	1,433
Net effect on other comprehensive income (loss)	635	(1,467)	(7,632)	(5,391)
Total other comprehensive (loss) income, net of tax	(1,692)	773	4,367	14,022
Total comprehensive income	$ 8,518	$ 15,641	$ 18,561	$ 52,857