Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 67,200	$ 72,886	$ 144,946	$ 145,686
Other comprehensive (loss) income:
Foreign currency translation adjustments	607	1,459	(7,808)	2,826
Change in unrealized (loss) gain on investments, net of income tax benefit (provision) of $639, $(514), $(574) and $(391) for the three and six months ended June 30, 2015 and 2014, respectively	(1,073)	2,674	1,040	1,762
Other comprehensive (loss) income	(466)	4,133	(6,768)	4,588
Comprehensive income	$ 66,734	$ 77,019	$ 138,178	$ 150,274