Accumulated Other Comprehensive Loss (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance	$ (79,917)		$ (114,213)		$ (80,923)		$ (116,840)
Other comprehensive income before reclassifications	0		(284)		0		180
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	59	[1]	107	[1]	177	[1]	314	[1]
Amounts reclassified from accumulated other comprehensive loss, Actuarial loss	441	[2]	1,179	[2]	1,329	[2]	3,135	[2]
Amounts reclassified from accumulated other comprehensive loss, tax	1,835		(3,047)		(341)		(7,286)
Ending balance	(79,417)		(113,211)		(79,417)		(113,211)
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss [Roll Forward]
Net current-period other comprehensive income	500		1,002		1,506		3,629
Gains and Losses on Derivatives
Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance			(338)				(1,009)
Other comprehensive income before reclassifications			(284)				180
Ending balance			(515)				(515)
Gains and Losses on Derivatives | Interest rate swaps
Accumulated Other Comprehensive Loss [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			107	[1]			314	[1]
Gains and Losses on Derivatives | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss, Actuarial loss			0	[2]			0	[2]
Net current-period other comprehensive income			(177)				494
Gains and Losses on Derivatives | Reclassification out of Accumulated Other Comprehensive Income | Interest rate swaps
Accumulated Other Comprehensive Loss [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss, tax			64				190
Defined Benefit Pension Items
Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance	(79,489)		(114,232)		(80,377)		(116,188)
Other comprehensive income before reclassifications	0		0		0		0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	[1]	0	[1]	0	[1]	0	[1]
Ending balance	(79,048)		(113,053)		(79,048)		(113,053)
Defined Benefit Pension Items | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss, Actuarial loss	441	[2]	1,179	[2]	1,329	[2]	3,135	[2]
Amounts reclassified from accumulated other comprehensive loss, tax	364		460		924		1,759
Net current-period other comprehensive income	441		1,179		1,329		3,135
Other
Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance	172		357		172		357
Other comprehensive income before reclassifications	0		0		0		0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	[1]	0	[1]	0	[1]	0	[1]
Ending balance	172		357		172		357
Other | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss, Actuarial loss	0	[2]	0	[2]	0	[2]	0	[2]
Net current-period other comprehensive income	0		0		0		0
Gain or Loss on Derivatives [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance	(600)				(718)
Other comprehensive income before reclassifications	0				0
Ending balance	(541)				(541)
Gain or Loss on Derivatives [Member] | Interest rate swaps
Accumulated Other Comprehensive Loss [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	59	[1]			177	[1]
Gain or Loss on Derivatives [Member] | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss, Actuarial loss	0	[2]			0	[2]
Net current-period other comprehensive income	59				177
Gain or Loss on Derivatives [Member] | Reclassification out of Accumulated Other Comprehensive Income | Interest rate swaps
Accumulated Other Comprehensive Loss [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss, tax	$ 37				$ 111

[1] (a) Interest rate swap is included in interest expense in the Condensed Consolidated Statements of Operations

[2] (b) Actuarial loss is included in defined benefit pension plan expense in the Condensed Consolidated Statements of Operations