Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenue	$ 706,508	$ 668,724
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	240,743	234,825
Research and development	66,141	65,065
Sales and marketing	126,276	122,553
General and administrative	122,835	154,385
Amortization of acquired intangible assets	9,599	8,431
Restructuring charges	6,389	14,908
Total costs and operating expenses	571,983	600,167
Income from operations	134,525	68,557
Interest income	8,635	3,965
Interest expense	(12,116)	(4,850)
Other income, net	511	21
Income before provision for income taxes	131,555	67,693
Provision for income taxes	24,425	13,979
Net income	$ 107,130	$ 53,714
Net income per share:
Basic (in dollars per share)	$ 0.66	$ 0.32
Diluted (in dollars per share)	$ 0.65	$ 0.31
Shares used in per share calculations:
Basic (in shares)	163,236	170,116
Diluted (in shares)	164,787	172,004