Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 9,293	$ 8,057	$ 19,818	$ 21,180
Other comprehensive income (loss), net of tax:
Change in fair value of interest rate swap agreements	(1,126)	474	(2,322)	(1,296)
Total other comprehensive income (loss)	(1,126)	474	(2,322)	(1,296)
Comprehensive income (loss)	$ 8,167	$ 8,531	$ 17,496	$ 19,884