Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	$ (1,395)	$ (1,059)
Accumulated other comprehensive income (loss), beginning balance	(82,876)	(29,818)	$ (117,287)
Other comprehensive income (loss) before reclassifications:
Actuarial gain (loss) for retiree liabilities	(31,895)	(90,180)	130,330
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax	(517)	(1,629)
Other Comprehensive Income (Loss), Finalization of Pension and Other Postretirement Benefit Plan Valuation, before Tax		11,660
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	181	570
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	7,462	319	12,715
Negative prior service cost (reclassified to salaries, wages and benefits)	(542)	(3,487)	(5,654)
Hedging gain (reclassified to interest expense)	(50)	(42)	(50)
Income Tax (Expense) or Benefit	46	37	21
Income Tax (Expense) or Benefit	9,406	30,301	(49,872)
Other comprehensive income (loss), net of tax	(4)	(5)	(29)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(336)	(1,059)	0
Other comprehensive income (loss), net of tax		(53,058)	87,469
Accumulated other comprehensive income (loss), ending balance	(99,012)	(82,876)	(29,818)
Total comprehensive income (loss)	25,086	(23,198)	67,841
Pension Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(81,191)	(31,072)	(121,602)
Other comprehensive income (loss) before reclassifications:
Actuarial gain (loss) for retiree liabilities	(32,640)	(90,400)	129,856
Other Comprehensive Income (Loss), Finalization of Pension and Other Postretirement Benefit Plan Valuation, before Tax		11,660
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	7,170	(2)	12,296
Income Tax (Expense) or Benefit	9,359	28,623	(51,622)
Other comprehensive income (loss), net of tax	(16,111)	(50,119)	90,530
Accumulated other comprehensive income (loss), ending balance	(97,302)	(81,191)	(31,072)
Post-Retirement Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(630)	1,245	4,277
Other comprehensive income (loss) before reclassifications:
Actuarial gain (loss) for retiree liabilities	745	220	474
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	292	321	419
Negative prior service cost (reclassified to salaries, wages and benefits)	(542)	(3,487)	(5,654)
Income Tax (Expense) or Benefit	(180)	1,071	1,729
Other comprehensive income (loss), net of tax	315	(1,875)	(3,032)
Accumulated other comprehensive income (loss), ending balance	(315)	(630)	1,245
Derivative [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	4	9	38
Amounts reclassified from accumulated other comprehensive income:
Accumulated other comprehensive income (loss), ending balance	$ 0	$ 4	$ 9