Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenue	$ 2,714,474	$ 2,489,035	$ 2,347,988
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	953,485	875,837	809,106
Research and development	246,165	222,434	167,628
Sales and marketing	517,353	481,522	427,885
General and administrative	574,067	509,165	439,916
Amortization of acquired intangible assets	33,311	30,904	26,642
Restructuring charge	27,594	54,884	10,301
Total costs and operating expenses	2,351,975	2,174,746	1,881,478
Income from operations	362,499	314,289	466,510
Interest income	26,940	17,855	14,702
Interest expense	(43,202)	(18,839)	(18,638)
Other (expense) income, net	(3,148)	887	3,788
Income before provision for income taxes	343,089	314,192	466,362
Provision for income taxes	44,716	91,426	145,635
Net income	$ 298,373	$ 222,766	$ 320,727
Net income per share:
Basic (in dollars per share)	$ 1.78	$ 1.30	$ 1.83
Diluted (in dollars per share)	$ 1.76	$ 1.29	$ 1.82
Shares used in per share calculations:
Basic (in shares)	167,312	171,559	174,917
Diluted (in shares)	169,188	172,711	176,215