Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	$ (1,364)	$ (1,440)	$ (1,348)	$ (1,477)
Accumulated other comprehensive income (loss), beginning balance	(63,020)	(79,866)
Other comprehensive income (loss) before reclassifications:
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax	(25)	58
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	9	(21)
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	942	2,008
Negative prior service cost (reclassified to salaries, wages and benefits)		(13)
Income Tax (Expense) or Benefit	(204)	(745)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(16)	37
Other comprehensive income (loss), net of tax		1,308
Accumulated other comprehensive income (loss), ending balance	(62,307)	(78,558)
Total comprehensive income (loss)	16,591	11,296
Pension Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(60,575)	(77,088)
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	887	1,937
Income Tax (Expense) or Benefit	(200)	(703)
Other comprehensive income (loss), net of tax	687	1,234
Accumulated other comprehensive income (loss), ending balance	(59,888)	(75,854)
Post-Retirement Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(1,097)	(1,301)
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	55	71
Negative prior service cost (reclassified to salaries, wages and benefits)		(13)
Income Tax (Expense) or Benefit	(13)	(21)
Other comprehensive income (loss), net of tax	42	37
Accumulated other comprehensive income (loss), ending balance	$ (1,055)	$ (1,264)