UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 24,712	$ 23,327	$ 71,091	$ 53,535
Other comprehensive income (loss) before taxes:
Change in fair value of interest rate swap agreements	4,037	350	5,223	13,377
Provision for income tax benefit (expense) related to components of other comprehensive income (loss)	(1,534)	(133)	(1,985)	(5,083)
Other comprehensive income (loss)	2,503	217	3,238	8,294
Comprehensive income (loss)	$ 27,215	$ 23,544	$ 74,329	$ 61,829