Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue	$ 709,912	$ 669,628	$ 2,121,494	$ 2,001,111
Costs and operating expenses:
Cost of revenue (exclusive of amortization of acquired intangible assets shown below)	246,938	239,246	729,874	709,558
Research and development	64,887	61,049	192,467	185,823
Sales and marketing	122,258	125,323	383,640	379,556
General and administrative	123,216	119,911	366,167	444,502
Amortization of acquired intangible assets	9,624	8,294	28,871	25,019
Restructuring (benefit) charges	(300)	(732)	6,879	14,442
Total costs and operating expenses	566,623	553,091	1,707,898	1,758,900
Income from operations	143,289	116,537	413,596	242,211
Interest income	7,908	9,258	22,953	19,632
Interest expense	(12,127)	(14,566)	(32,689)	(28,620)
Other expense, net	(752)	(459)	(819)	(3,207)
Income before provision for income taxes	138,318	110,770	403,041	230,016
Benefit (provision) for income taxes	960	(3,187)	(42,718)	(25,658)
Loss from equity method investment	(1,388)	0	(1,388)	0
Net income	$ 137,890	$ 107,583	$ 358,935	$ 204,358
Net income per share:
Basic (in dollars per share)	$ 0.85	$ 0.65	$ 2.20	$ 1.21
Diluted (in dollars per share)	$ 0.84	$ 0.64	$ 2.18	$ 1.20
Shares used in per share calculations:
Basic (in shares)	162,445	165,924	163,029	168,763
Diluted (in shares)	164,558	167,900	164,788	170,732