Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 5,717	$ 5,241	$ 7,987	$ 10,525
Other comprehensive income (loss), net of tax:
Change in fair value of interest rate swap agreements	86	(26)	(546)	(1,196)
Total other comprehensive income (loss)	86	(26)	(546)	(1,196)
Comprehensive income	$ 5,803	$ 5,215	$ 7,441	$ 9,329