Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (4,387)	$ 1,425	$ 2,518
Net change in unrealized gains (losses) on securities available-for-sale:
Unrealized gain (losses)	(85)	309	847
Expense (benefit) due to enactment of federal tax reform	44
Income tax effect	(14)	(105)	(372)
Unrealized gains on securities, net	(55)	204	475
Pension benefit liability adjustment:
Net gain (loss) during the period	(2,006)	456	(1,829)
Reclassification adjustments for amortization of prior service cost and net gain included in net periodic pension cost			245
Expense (benefit) due to enactment of federal tax reform	1,192
Income tax effect	(732)	(155)	53
Pension liability adjustment, net of tax	(1,546)	301	(1,531)
Total other comprehensive income (loss), net of tax	(1,601)	505	(1,056)
Total comprehensive income (loss)	$ (5,988)	$ 1,930	$ 1,462