Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance		$ (93,347)	$ (89,802)
Other comprehensive income before reclassifications		0	0
Ending balance		(92,668)	(89,108)
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss, Interest rate swap	[1]		59
Amounts reclassified from accumulated other comprehensive loss, Actuarial gain (loss)	[2]	679	635
Net current-period other comprehensive income		679	694
Gains and Losses on Derivatives
Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance		0	(242)
Other comprehensive income before reclassifications		0	0
Ending balance		0	(183)
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 gain (loss)	[2]	0	0
Net current-period other comprehensive income		0	59
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, Interest rate swap	[1]		59
Amounts reclassified from accumulated other comprehensive loss, Interest rate swap, tax			37
Defined Benefit Pension Items
Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance		(93,676)	(89,740)
Other comprehensive income before reclassifications		0	0
Ending balance		(92,981)	(89,098)
Defined Benefit Pension Items | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss, Interest rate swap	[1]		0
Amounts reclassified from accumulated other comprehensive loss, Actuarial gain (loss)	[2]	695	642
Amounts reclassification from accumulated other comprehensive loss, Actuarial gain (loss), tax		423	396
Net current-period other comprehensive income		695	642
Other
Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance		329	180
Other comprehensive income before reclassifications		0	0
Ending balance		313	173
Other | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Loss [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss, Interest rate swap	[1]		0
Amounts reclassified from accumulated other comprehensive loss, Actuarial gain (loss)	[2]	(16)	(7)
Net current-period other comprehensive income		$ (16)	$ (7)

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

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