Other Comprehensive (Loss) Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Other Comprehensive Loss, Before Tax [Abstract]
Foreign currency translation adjustment	$ 166	$ (54)	$ 25
Reclassification of net gains on derivative instruments to net income	(1,188)	(1,188)	(1,188)
Reclassification of deferred tax liability on net gains on derivative instruments	0	0	0
Pension and postretirement medical liability adjustment	1,568	(897)	(736)
Other comprehensive loss, before tax	546	(2,139)	(1,899)
Other Comprehensive Loss, Tax [Abstract]
Foreign currency translation adjustment	0	0	0
Reclassification of net gains on derivative instruments to net income	458	456	458
Reclassification of deferred tax liability on net gains on derivative instruments	0	0	(3,572)
Pension and postretirement medical liability adjustment	(605)	344	155
Other comprehensive loss, tax	(147)	800	(2,959)
Other Comprehensive Loss, Net of Tax [Abstract]
Foreign currency translation adjustment	166	(54)	25
Reclassification of net gains on derivative instruments to net income	(730)	(732)	(730)
Reclassification of deferred tax liability on net gains on derivative instruments	0	0	(3,572)
Postretirement medical liability adjustment	963	(553)	(581)
Other comprehensive loss, net of tax	399	(1,339)	(4,858)
Accumulated Other Comprehensive Income, Net of Tax [Abstract]
Foreign currency translation	532	366
Derivative instruments designated as cash flow hedges	3,513	4,243
Pension and postretirement medical plans	(1,329)	(2,292)
Accumulated other comprehensive income	2,716	2,317
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Other Comprehensive Loss, Net of Tax [Abstract]
Foreign currency translation adjustment	0
Reclassification of net gains on derivative instruments to net income	(730)
Postretirement medical liability adjustment	0
Other comprehensive loss, net of tax	(730)
Accumulated Other Comprehensive Income, Net of Tax [Abstract]
Accumulated other comprehensive income	3,513	4,243
Accumulated Defined Benefit Plans Adjustment [Member]
Other Comprehensive Loss, Net of Tax [Abstract]
Foreign currency translation adjustment	0
Reclassification of net gains on derivative instruments to net income	0
Postretirement medical liability adjustment	963
Other comprehensive loss, net of tax	963
Accumulated Other Comprehensive Income, Net of Tax [Abstract]
Accumulated other comprehensive income	(1,329)	(2,292)
Foreign Currency Gain (Loss) [Member]
Other Comprehensive Loss, Net of Tax [Abstract]
Foreign currency translation adjustment	166
Reclassification of net gains on derivative instruments to net income	0
Postretirement medical liability adjustment	0
Other comprehensive loss, net of tax	166
Accumulated Other Comprehensive Income, Net of Tax [Abstract]
Accumulated other comprehensive income	$ 532	$ 366