Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 5,241	$ 8,735	$ 10,525	$ 13,123
Other comprehensive income (loss), net of tax:
Change in fair value of interest rate swap agreements	(26)	(1,139)	(1,196)	(1,770)
Total other comprehensive income (loss)	(26)	(1,139)	(1,196)	(1,770)
Comprehensive income (loss)	$ 5,215	$ 7,596	$ 9,329	$ 11,353