CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (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 (loss)	$ 22,822	$ 14,781	$ 37,446	$ 28,749
Other comprehensive income (loss) before taxes:
Change in fair value of interest rate swap agreements	(2,798)	1,439	(7,676)	(50)
Provision for income tax benefit (expense) related to components of other comprehensive income (loss)	1,063	(547)	2,916	19
Other comprehensive income (loss)	(1,735)	892	(4,760)	(31)
Comprehensive income (loss)	$ 21,087	$ 15,673	$ 32,686	$ 28,718