Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Other Comprehensive Income [Abstract]
NET INCOME	$ 32,765	$ 31,335	$ 92,271	$ 83,077
Other comprehensive income (loss), net of taxes:
Foreign currency translation adjustment	3,237	1,856	(23,487)	1,850
Unrealized loss on marketable securities, net of tax benefit of $0, $10, $0 and $5, respectively	0	(16)	0	(8)
Net unrealized gain (loss) on interest rate swaps:
Unrealized gain (loss) arising during the period, net of tax benefit (provision) of $1,615, $2,786, ($2,999) and $7,352, respectively	(2,691)	(4,644)	4,999	(12,254)
Reclassification adjustment for loss included in interest expense, net of tax provision of $1,075, $1,006, $3,120 and $3,216, respectively	1,791	1,676	5,200	5,360
Net unrealized gain (loss) on interest rate swaps, net of tax	(900)	(2,968)	10,199	(6,894)
OTHER COMPREHENSIVE INCOME (LOSS) NET OF TAXES	2,337	(1,128)	(13,288)	(5,052)
COMPREHENSIVE INCOME	35,102	30,207	78,983	78,025
Total [Member]
Statement of Other Comprehensive Income [Abstract]
NET INCOME	$ 32,765	$ 31,335	$ 92,271	$ 83,077