Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income	$ 38,471	$ 31,157	$ 10,941
Available-for-sale investment securities:
Gross unrealized holding (loss) gain arising in the period	(555)	(2,590)	1,232
Related tax benefit (expense)	195	906	(431)
Less: reclassification adjustment for net gain included in net income	2,983	930	729
Related tax expense	(1,044)	(326)	(255)
Amounts reclassified out of accumulated other comprehensive (loss) income per ASU 2018-02	924
Amounts reclassified out of accumulated other comprehensive (loss) income per ASU 2018-02	(370)	0	0
Net effect on other comprehensive (loss) income	(2,669)	(2,288)	327
Defined benefit plans:
Net (loss) gain arising during the period	(616)	(232)	373
Related tax benefit (expense)	216	81	(130)
Amortization of unrecognized loss and service cost on benefit plans	96	89	112
Related tax expense	(34)	(31)	(38)
Recognition of loss due to settlement and curtailment	242	0	459
Related tax expense	(85)	0	(161)
Amounts reclassified out of accumulated other comprehensive (loss) income per ASU 2018-02	(754)	0	0
Net effect on other comprehensive (loss) income	(935)	(93)	615
Net (loss) gain arising during the period	(395)	1,824	0
Related tax benefit (expense)	138	(638)	0
Amounts reclassified out of accumulated other comprehensive (loss) income per ASU 2018-02	200	0	0
Net effect on other comprehensive (loss) income	(57)	1,186	0
Total other comprehensive (loss) income, net of tax	(3,661)	(1,195)	942
Total comprehensive income	$ 34,810	$ 29,962	$ 11,883