Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 7,962	$ 4,913	$ 15,957	$ 4,224
Available-for-sale investment securities:
Gross unrealized holding gain (loss) arising in the period	6,421	(6,596)	18,750	2,287
Related tax (benefit) expense	(2,247)	2,308	(6,563)	(800)
Less: reclassification adjustment for net gain included in net income	767	11	863	611
Related tax expense	(268)	(4)	(302)	(214)
Net effect on other comprehensive income (loss)	3,675	(4,295)	11,626	1,090
Defined benefit plans:
Net gain arising during the period	2	533	2	507
Related tax expense	(1)	(186)	(1)	(177)
Amortization of unrecognized loss and service cost on benefit plans	46	30	45	62
Related tax expense	(16)	(9)	(15)	(21)
Recognition of loss due to settlement and curtailment	0	103	0	372
Related tax expense	0	(36)	0	(130)
Net effect on other comprehensive income	31	435	31	613
Cash flow hedges:
Net loss arising during the period	(252)	0	(252)	0
Related tax benefit	88	0	88	0
Net effect on other comprehensive loss	(164)	0	(164)	0
Total other comprehensive income (loss), net of tax expense	3,542	(3,860)	11,493	1,703
Total comprehensive income	$ 11,504	$ 1,053	$ 27,450	$ 5,927