Accumulated Other Comprehensive Loss (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Components of comprehensive income
Net income	$ 2,757	$ 4,624
Reclassification to interest expense	294	339
Deferred income tax expense	(107)	(82)
Mark-to-market of interest rate hedges		(112)
Comprehensive income	2,944	4,769
Accumulated other comprehensive loss
Mark-to-market of interest rate hedges, net of tax benefit	(1,487)		(1,674)
Minimum pension liability adjustments, net of tax benefit	(718)		(718)
Accumulated other comprehensive loss	$ (2,205)		$ (2,392)