Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Net income	$ 66,667	$ 75,989	$ 145,286	$ 127,517
Change in fair value of interest rate swap contracts
Unrealized holding losses arising during the period on effective hedges, net of income tax benefit of $120 and $242, respectively		(212)		(430)
Less: Reclassification adjustments for losses included in net income, net of income taxes of $1,546 and $3,852, respectively		2,707		6,835
Change in fair value of interest rate swap contracts, net		2,495		6,405
Foreign currency translation adjustment during the period	(455)	122	(167)	497
Unrealized holding gains on corporate debt securities arising during the period	155	578	85	910
Other comprehensive (loss) income	(300)	3,195	(82)	7,812
Comprehensive income	$ 66,367	$ 79,184	$ 145,204	$ 135,329