Commitments and Contingencies - Narrative (Detail) $ in Thousands		12 Months Ended
		Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)		Dec. 31, 2016 USD ($)		May 31, 2018 USD ($) ft²	Jun. 30, 2017 USD ($)
Operating Leased Assets [Line Items]
Total minimum lease payments		$ 898,851
Rent expense		42,800	$ 39,700		$ 34,200
Letters of credit		22,600
Legal settlements	[1]	0	0	[2]	270,000	[2]
Cost of revenues
Operating Leased Assets [Line Items]
Service charges and operating lease expense		25,700	22,500		$ 17,300
2022 Notes
Operating Leased Assets [Line Items]
Notes, par value		$ 782,500	$ 782,500					$ 782,500
Santa Clara Office
Operating Leased Assets [Line Items]
Area of building under lease (in sq. ft) | ft²							838,523
Lease term							5 years
Total minimum lease payments							$ 566,500

[1] Includes stock-based compensation as follows:   Year Ended December 31,   2018   2017   2016       *As Adjusted   *As Adjusted Cost of revenues:           Subscription $ 48,738
  $ 35,334
  $ 28,420
Professional services and other 32,816
  27,401
  26,516
Sales and marketing 228,045
  170,527
  131,571
Research and development 135,203
  92,025
  81,731
General and administrative 99,151
  68,717
  49,416

[2] As adjusted to reflect the impact of the full retrospective adoption of Topic 606.