Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statements Other Comprehensive Income [Abstract]
Net income	$ 147,335	$ 107,896	$ 89,052
Other Comprehensive (Loss) Income:
Fair value of interest rate swaps, net of tax		3,957	2,731
Foreign currency translation adjustment (loss) gain, net of tax	(5,615)	115	4,374
Total other comprehensive (loss) income	(5,615)	4,072	7,105
Total comprehensive income	$ 141,720	$ 111,968	$ 96,157