Accumulated Other Comprehensive Loss (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Components of comprehensive income
Net income	$ 4,626	$ 4,060	$ 7,382	$ 8,684
Reclassification to interest expense	292	335	586	674
Deferred income tax expense	(122)	(52)	(229)	(134)
Mark-to-market of interest rate hedge	43	(193)	43	(305)
Comprehensive income	4,839	4,150	7,782	8,919
Accumulated other comprehensive loss
Mark to market of interest rate hedges, net of tax benefit	(1,274)		(1,274)		(1,674)
Minimum pension liability adjustments, net of tax benefit	(718)		(718)		(718)
Accumulated other comprehensive loss	$ (1,992)		$ (1,992)		$ (2,392)