Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenue	$ 668,724	$ 600,293
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	234,825	205,727
Research and development	65,065	52,162
Sales and marketing	122,553	114,492
General and administrative	154,385	115,009
Amortization of acquired intangible assets	8,431	7,569
Restructuring charges	14,908	0
Total costs and operating expenses	600,167	494,959
Income from operations	68,557	105,334
Interest income	3,965	4,624
Interest expense	(4,850)	(4,597)
Other income (expense), net	21	(684)
Income before provision for income taxes	67,693	104,677
Provision for income taxes	13,979	30,094
Net income	$ 53,714	$ 74,583
Net income per share:
Basic (in dollars per share)	$ 0.32	$ 0.43
Diluted (in dollars per share)	$ 0.31	$ 0.43
Shares used in per share calculations:
Basic (in shares)	170,116	173,158
Diluted (in shares)	172,004	175,171