Consolidated Statements of Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Total revenues		$ 3,460,437	$ 2,608,816	$ 1,918,494
Cost of revenues:
Total cost of revenues	[1]	796,645	622,658	499,862
Gross profit	[1]	2,663,792	1,986,158	1,418,632
Operating expenses:
Sales and marketing	[1]	1,534,284	1,203,056	894,977
Research and development	[1]	748,369	529,501	377,518
General and administrative	[1]	339,016	296,027	210,533
Total operating expenses	[1]	2,621,669	2,028,584	1,483,028
Income (loss) from operations		42,123	(42,426)	(64,396)
Interest expense		(33,283)	(52,733)	(53,394)
Interest income and other income (expense), net		58,345	56,135	4,384
Income (loss) before income taxes		67,185	(39,024)	(113,406)
(Benefit from) provision for income taxes		(559,513)	(12,320)	3,440
Net income (loss)		$ 626,698	$ (26,704)	$ (116,846)
Net income (loss) per share - basic (in USD per share)		$ 3.36	$ (0.15)	$ (0.68)
Net income (loss) per share - diluted (in USD per share)		$ 3.18	$ (0.15)	$ (0.68)
Weighted-average shares used to compute net income (loss) per share - basic (in shares)		186,466	177,846	171,176
Weighted-average shares used to compute net income (loss) per share - diluted (in shares)		197,223	177,846	171,176
Other comprehensive income (loss):
Foreign currency translation adjustments		$ 20,539	$ (1,903)	$ 23,064
Unrealized gains (losses) on investments, net of tax		8,751	(665)	5,376
Other comprehensive income (loss)		29,290	(2,568)	28,440
Comprehensive income (loss)		655,988	(29,272)	(88,406)
Subscription
Revenues:
Total revenues		3,255,079	2,421,313	1,739,500
Cost of revenues:
Total cost of revenues	[1]	549,642	417,421	315,570
Professional services and other
Revenues:
Total revenues		205,358	187,503	178,994
Cost of revenues:
Total cost of revenues	[1]	$ 247,003	$ 205,237	$ 184,292

[1] Includes stock-based compensation as follows:   Year Ended December 31,   2019   2018   2017 Cost of revenues:           Subscription $ 72,728
  $ 48,738
  $ 35,334
Professional services and other 43,123
  32,816
  27,401
Sales and marketing 268,408
  228,045
  170,527
Research and development 194,821
  135,203
  92,025
General and administrative 83,115
  99,151
  68,717