Other Comprehensive (Loss) Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other Comprehensive Loss, Before Tax [Abstract]
Foreign currency tanslation adjustment, before tax	$ (54)	$ 25	$ 111
Reclassification of net gains on derivative instruments to net income, before tax	(1,188)	(1,188)	(1,188)
Reclassification of deferred tax liability on net gains on derivative instruments, before tax		0
Pension and postretirement medical liability adjustment, before tax	(897)	(736)	(209)
Other comprehensive loss, before tax	(2,139)	(1,899)	(1,286)
Other Comprehensive Loss, Tax [Abstract]
Foreign currency translation adjustment, tax	0	0	0
Reclassification of net gains on derivative instruments to net income, tax	456	458	0
Reclassification of deferred tax liability on net gains on derivative instruments, tax		(3,572)
Pension and postretirement medical liability adjustment, tax	344	155	75
Other comprehensive loss, tax	800	(2,959)	75
Other Comprehensive Loss, Net of Tax [Abstract]
Foreign currency translation adjustment, net of tax	(54)	25	111
Reclassification of net gains on derivative instruments	(732)	(730)	(1,188)
Reclassification of deferred tax liability on net gains on derivative instruments, net of tax	0	(3,572)	0
Pension and postretirement medical liability adjustment, net of tax	(553)	(581)	(134)
Other comprehensive loss, net of tax	(1,339)	(4,858)	(1,211)
Accumulated Other Comprehensive Income, Net of Tax [Abstract]
Foreign currency translation	366	420
Derivative instruments designated as cash flow hedges	4,243	4,975
Pension and postretirement medical plans	(2,292)	(1,739)
Accumulated other comprehensive income	2,317	3,656
Accumulated Other Comprehensive Income [Member]
Other Comprehensive Loss, Net of Tax [Abstract]
Foreign currency translation adjustment, net of tax	(54)	25	111
Reclassification of net gains on derivative instruments	(732)	(730)	(1,188)
Reclassification of deferred tax liability on net gains on derivative instruments, net of tax		(3,572)
Pension and postretirement medical liability adjustment, net of tax	$ (553)	$ (581)	$ (134)