Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 72,886	$ 61,895	$ 145,686	$ 133,382
Other comprehensive income (loss):
Foreign currency translation adjustments	1,459	(3,746)	2,826	(7,760)
Change in unrealized gain (loss) on investments, net of income tax (provision) benefit of $(514), $913, $(391), and $62 for the three and six months ended June 30, 2014 and 2013, respectively	2,674	(1,626)	1,762	(1,555)
Other comprehensive income (loss)	4,133	(5,372)	4,588	(9,315)
Comprehensive income	$ 77,019	$ 56,523	$ 150,274	$ 124,067