Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Schedule of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax		$ (5,821)		$ (5,821)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	$ (1,465)	(1,356)	$ (1,465)	(1,356)	$ (1,487)	$ (1,348)	$ (1,341)	$ (1,477)
Accumulated other comprehensive income (loss), beginning balance	(61,701)	(77,187)	(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	33	(24)	(178)	186
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax		12,923		12,923
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	(11)	9	61	(65)
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	942	2,015	2,826	6,032
Negative prior service cost (reclassified to salaries, wages and benefits)		(13)		(39)
Income Tax (Expense) or Benefit	(223)	(3,295)	(577)	(4,817)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	22	(15)	(117)	121
Other comprehensive income (loss), net of tax		5,785
Accumulated other comprehensive income (loss), ending balance	(60,949)	(71,402)	(60,949)	(71,402)
Total comprehensive income (loss)	33,855	(27,099)	75,686	(68,158)
Pension Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax		(5,821)		(5,821)
Accumulated other comprehensive income (loss), beginning balance	(59,201)	(74,619)	(60,575)	(77,088)
Other comprehensive income (loss) before reclassifications:
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), before Tax		12,923		12,923
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	887	1,944	2,661	5,819
Income Tax (Expense) or Benefit	(200)	(3,283)	(600)	(4,689)
Other comprehensive income (loss), net of tax	687	5,763	2,061	8,232
Accumulated other comprehensive income (loss), ending balance	(58,514)	(68,856)	(58,514)	(68,856)
Post-Retirement Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(1,013)	(1,227)	(1,097)	(1,301)
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	55	71	165	213
Negative prior service cost (reclassified to salaries, wages and benefits)		(13)		(39)
Income Tax (Expense) or Benefit	(12)	(21)	(38)	(63)
Other comprehensive income (loss), net of tax	43	37	127	111
Accumulated other comprehensive income (loss), ending balance	(970)	$ (1,190)	(970)	(1,190)
AOCI Attributable to Parent [Member]
Amounts reclassified from accumulated other comprehensive income:
Total comprehensive income (loss)	$ 752		$ 2,071	$ 8,464