Changes in Accumulated Other Comprehensive Loss by Component (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Changes to accumulated other comprehensive loss by component
Balance at the beginning of the period	$ (862)	$ (7,084)
Other comprehensive earning (loss) before reclassifications	(5,231)	5,198
Amounts reclassified from accumulated other comprehensive loss	65	1,024
Balance at the end of the period	(6,028)	(862)
Unrealized Net Loss on Interest Rate Swap
Changes to accumulated other comprehensive loss by component
Balance at the beginning of the period	(184)	(344)
Other comprehensive earning (loss) before reclassifications	(2)	(22)
Amounts reclassified from accumulated other comprehensive loss	186	182
Balance at the end of the period		(184)
Other Postretirement Benefit Liability
Changes to accumulated other comprehensive loss by component
Balance at the beginning of the period	2,234	1,063
Other comprehensive earning (loss) before reclassifications	(1,180)	1,066
Amounts reclassified from accumulated other comprehensive loss	(247)	105
Balance at the end of the period	807	2,234
Pension Liability
Changes to accumulated other comprehensive loss by component
Balance at the beginning of the period	(2,912)	(7,803)
Other comprehensive earning (loss) before reclassifications	(4,049)	4,154
Amounts reclassified from accumulated other comprehensive loss	126	737
Balance at the end of the period	$ (6,835)	$ (2,912)