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 Income And Comprehensive Income [Abstract]
Net income	$ 78,620	$ 59,648	$ 216,381	$ 156,128
Other comprehensive income:
Foreign currency translation adjustment gain (loss), net of tax	18,293	8,774	(15,861)	8,649
Total other comprehensive income (loss)	18,293	8,774	(15,861)	8,649
Total comprehensive income	$ 96,913	$ 68,422	$ 200,520	$ 164,777