Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income Loss [Line Items]
Other comprehensive income (loss), net of tax	$ (1,601)	$ 505
Unrealized gains (losses) on securities available for sale
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) beginning balance	(166)	(370)
Other comprehensive income (loss), net of tax	(55)	204
Accumulated other comprehensive income (loss) ending balance	(221)	(166)
Unrealized gains (losses) on pension benefits
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) beginning balance	(6,084)	(6,385)
Other comprehensive income (loss), net of tax	(1,546)	301
Accumulated other comprehensive income (loss) ending balance	(7,630)	(6,084)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss) beginning balance	(6,250)	(6,755)
Accumulated other comprehensive income (loss) ending balance	$ (7,851)	$ (6,250)