Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Condensed Consolidated Statements of Comprehensive Income [Abstract]
Net income (loss)	$ 10,042	$ 19,401	$ 58,719	$ 55,716
Other comprehensive income (loss) before taxes:
Change in fair value of interest rate swap agreements	(194)	(4,239)	(133)	(5,902)
Total other comprehensive income (loss) before taxes	(194)	(4,239)	(133)	(5,902)
Provision for income tax benefit (expense) related to components of other comprehensive income (loss)	72	1,611	50	2,242
Other comprehensive income (loss)	(122)	(2,628)	(83)	(3,660)
Comprehensive income (loss)	$ 9,920	$ 16,773	$ 58,636	$ 52,056