Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 10,941	$ 16,684	$ 17,574
Available-for-sale investment securities:
Gross unrealized holding gain (loss) arising in the period	1,232	19,326	(25,130)
Related tax (expense) benefit	(431)	(6,764)	8,795
Less: reclassification adjustment for net gain included in net income	729	398	489
Related tax expense	(255)	(139)	(171)
Net effect on other comprehensive income (loss)	327	12,303	(16,653)
Defined benefit plans:
Net gain (loss) arising during the period	373	(2,083)	3,788
Related tax (expense) benefit	(130)	729	(1,326)
Amortization of unrecognized loss and service cost on benefit plans	112	129	182
Related tax expense	(38)	(45)	(64)
Recognition of loss due to settlement and curtailment	459	1,400	270
Related tax expense	(161)	(490)	(95)
Net effect on other comprehensive income (loss)	615	(360)	2,755
Total other comprehensive income (loss), net of tax	942	11,943	(13,898)
Total comprehensive income	$ 11,883	$ 28,627	$ 3,676