Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components of comprehensive income
Net income (loss)	$ 2,286	$ 5,676	$ 2,559	$ 2,365	$ 3,731	$ 5,426	$ 5,718	$ 4,492	$ 12,886	$ 19,367	$ 14,800
Minimum pension liability adjustments									946	(127)	309
Reclassification to interest expense									678	921	1,141
Deferred income tax expense									(585)	(271)	(510)
Mark to market of interest rate hedges									(15)	(49)	(46)
Comprehensive income									$ 13,910	19,841	$ 15,694
Accumulated other comprehensive loss
Mark to market of interest rate hedges, net of tax benefit					(422)					(422)
Minimum pension liability adjustments, net of tax benefit					(602)					(602)
Accumulated other comprehensive loss					$ (1,024)					$ (1,024)