Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 74,858	$ 77,746
Other comprehensive income (loss):
Foreign currency translation adjustments	9,653	(8,415)
Unrealized gains on investments, net of income tax provision of $1,783 and $1,213 for the three months ended March 31, 2016 and 2015, respectively	3,008	2,113
Other comprehensive income (loss)	12,661	(6,302)
Comprehensive income	$ 87,519	$ 71,444