Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017	Mar. 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	$ (1,487)	$ (1,341)	$ (1,487)	$ (1,341)	$ (1,364)	$ (1,348)	$ (1,440)	$ (1,477)
Accumulated other comprehensive income (loss), beginning balance	(62,307)	(78,558)	(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	(186)	152	(211)	210
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	63	(53)	72	(74)
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	942	2,008	1,884	4,016
Negative prior service cost (reclassified to salaries, wages and benefits)		(13)		(26)
Income Tax (Expense) or Benefit	(150)	(776)	(354)	(1,521)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(123)	99	(139)	136
Other comprehensive income (loss), net of tax		1,371
Accumulated other comprehensive income (loss), ending balance	(61,701)	(77,187)	(61,701)	(77,187)
Total comprehensive income (loss)	25,240	(52,355)	41,831	(41,059)
Pension Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(59,888)	(75,854)	(60,575)	(77,088)
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	887	1,937	1,774	3,874
Income Tax (Expense) or Benefit	(200)	(702)	(400)	(1,405)
Other comprehensive income (loss), net of tax	687	1,235	1,374	2,469
Accumulated other comprehensive income (loss), ending balance	(59,201)	(74,619)	(59,201)	(74,619)
Post-Retirement Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(1,055)	(1,264)	(1,097)	(1,301)
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	55	71	110	142
Negative prior service cost (reclassified to salaries, wages and benefits)		(13)		(26)
Income Tax (Expense) or Benefit	(13)	(21)	(26)	(42)
Other comprehensive income (loss), net of tax	42	37	84	74
Accumulated other comprehensive income (loss), ending balance	(1,013)	$ (1,227)	(1,013)	(1,227)
AOCI Attributable to Parent [Member]
Amounts reclassified from accumulated other comprehensive income:
Total comprehensive income (loss)	$ 606		$ 1,319	$ 2,679