Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	$ (14)	$ (12)	$ (1,479)	$ (1,348)
Accumulated other comprehensive income (loss), beginning balance	(61,866)	(91,362)	(63,020)
Other comprehensive income (loss) before reclassifications:
Actuarial gain (loss) for retiree liabilities	(25,638)	20,800	(40,934)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax	(2)	(18)	(171)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, before Tax		2,253
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	0	(768)	40
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	3,887	15,700	3,766
Income Tax (Expense) or Benefit	4,963	(9,239)	8,997
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(2)	1,467	(131)
Other comprehensive income (loss), net of tax		29,496	(28,342)
Accumulated other comprehensive income (loss), ending balance	(78,656)	(61,866)	(91,362)
Total comprehensive income (loss)	15,325	90,698	40,943
Pension Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(61,152)	(89,042)	(60,575)
Other comprehensive income (loss) before reclassifications:
Actuarial gain (loss) for retiree liabilities	(25,712)	20,793	(41,051)
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	3,763	15,528	3,547
Income Tax (Expense) or Benefit	5,008	(8,431)	9,037
Other comprehensive income (loss), net of tax	(16,941)	27,890	(28,467)
Accumulated other comprehensive income (loss), ending balance	(78,093)	(61,152)	(89,042)
Post-Retirement Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(702)	(841)	(1,097)
Other comprehensive income (loss) before reclassifications:
Actuarial gain (loss) for retiree liabilities	74	7	117
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	124	172	219
Income Tax (Expense) or Benefit	(45)	(40)	(80)
Other comprehensive income (loss), net of tax	153	139	256
Accumulated other comprehensive income (loss), ending balance	$ (549)	$ (702)	$ (841)