Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	$ (1,059)
Accumulated other comprehensive income (loss), beginning balance	(29,818)	(117,287)	(103,047)
Other comprehensive income (loss) before reclassifications:
Actuarial gain (loss) for retiree liabilities	(90,180)	130,330	(27,350)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax	(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	570
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	319	12,715	11,114
Negative prior service cost (reclassified to salaries, wages and benefits)	(3,487)	(5,654)	(5,552)
Hedging gain (reclassified to interest expense)	(42)	(50)	(57)
Income Tax (Expense) or Benefit	37	21	20
Income Tax (Expense) or Benefit	30,301	(49,872)	7,605
Other comprehensive income (loss), net of tax	(5)	(29)	(37)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(1,059)	0	0
Other comprehensive income (loss), net of tax		87,469	(14,240)
Accumulated other comprehensive income (loss), ending balance	(82,876)	(29,818)	(117,287)
Total comprehensive income (loss)	(23,198)	67,841	26,634
Pension Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(31,072)	(121,602)	(110,626)
Other comprehensive income (loss) before reclassifications:
Actuarial gain (loss) for retiree liabilities	(90,400)	129,856	(27,518)
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)	(2)	12,296	10,681
Income Tax (Expense) or Benefit	28,623	(51,622)	5,861
Other comprehensive income (loss), net of tax	(50,119)	90,530	(10,976)
Accumulated other comprehensive income (loss), ending balance	(81,191)	(31,072)	(121,602)
Post-Retirement Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	1,245	4,277	7,504
Other comprehensive income (loss) before reclassifications:
Actuarial gain (loss) for retiree liabilities	220	474	168
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	321	419	433
Negative prior service cost (reclassified to salaries, wages and benefits)	(3,487)	(5,654)	(5,552)
Income Tax (Expense) or Benefit	1,071	1,729	1,724
Other comprehensive income (loss), net of tax	(1,875)	(3,032)	(3,227)
Accumulated other comprehensive income (loss), ending balance	(630)	1,245	4,277
Derivative [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance				75
Amounts reclassified from accumulated other comprehensive income:
Accumulated other comprehensive income (loss), ending balance	$ 4	$ 9	$ 38	$ 75