CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (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)	$ 14,781	$ 26,993	$ 28,749	$ 46,379
Other comprehensive income (loss) before taxes:
Change in fair value of interest rate swap agreements	1,439	(487)	(50)	1,186
Provision for income tax benefit (expense) related to components of other comprehensive income (loss)	(547)	185	19	(451)
Other comprehensive income (loss)	892	(302)	(31)	735
Comprehensive income (loss)	$ 15,673	$ 26,691	$ 28,718	$ 47,114