Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Revenue	$ 609,237	$ 567,725
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	205,703	194,736
Research and development	52,162	40,842
Sales and marketing	113,566	102,211
General and administrative	115,009	102,283
Amortization of acquired intangible assets	7,569	6,716
Restructuring charges	0	6,818
Total costs and operating expenses	494,009	453,606
Income from operations	115,228	114,119
Interest income	4,624	3,320
Interest expense	(4,597)	(4,653)
Other expense, net	(684)	(189)
Income before provision for income taxes	114,571	112,597
Provision for income taxes	33,641	37,739
Net income	$ 80,930	$ 74,858
Net income per share:
Basic (in dollars per share)	$ 0.47	$ 0.42
Diluted (in dollars per share)	$ 0.46	$ 0.42
Shares used in per share calculations:
Basic (in shares)	173,158	176,403
Diluted (in shares)	175,171	177,539