Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Pension Plans [Member]	Mar. 31, 2013 Pension Plans [Member]	Mar. 31, 2014 Post-Retirement Plans [Member]	Mar. 31, 2013 Post-Retirement Plans [Member]	Mar. 31, 2014 Derivative [Member]	Dec. 31, 2013 Derivative [Member]	Mar. 31, 2013 Derivative [Member]	Dec. 31, 2012 Derivative [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	$ (29,818)	$ (117,287)	$ (31,072)	$ (121,602)	$ 1,245	$ 4,277	$ 2	$ 9	$ 30	$ 38
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	79	3,178	(1)	3,074	80	104
Negative prior service cost (reclassified to salaries, wages and benefits)	(872)	(1,413)			(872)	(1,413)
Hedging gain (reclassified to interest expense)	(11)	(13)
Income Tax (Expense) or Benefit			0	(1,116)	288	475
Income Tax (Expense) or Benefit	4	5
Income Tax (Expense) or Benefit	292	(636)
Other comprehensive income (loss), net of tax			(1)	1,958	(504)	(834)
Other comprehensive income (loss), net of tax	(7)	(8)
Other comprehensive income (loss), net of tax	(512)	1,116
Accumulated other comprehensive income (loss), ending balance	$ (30,330)	$ (116,171)	$ (31,073)	$ (119,644)	$ 741	$ 3,443	$ 2	$ 9	$ 30	$ 38