Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 91,155	$ 79,756	$ 236,841	$ 213,138
Other comprehensive (loss) income:
Foreign currency translation adjustments	(10,763)	2,950	(7,937)	(4,810)
Change in unrealized (loss) gain on investments, net of income tax benefit (provision) of $715, $(1,532), $324, and $(629) for the three and nine months ended September 30, 2014 and 2013, respectively	(1,279)	2,571	483	1,016
Other comprehensive (loss) income	(12,042)	5,521	(7,454)	(3,794)
Comprehensive income	$ 79,113	$ 85,277	$ 229,387	$ 209,344