Equity Incentive Plans - 2015 Employee Stock Purchase Plan (Details)		1 Months Ended		12 Months Ended
	Mar. 16, 2016	Feb. 28, 2019 USD ($)	Aug. 31, 2015 USD ($) shares	Feb. 02, 2020 USD ($) numberOfFinancialInstitutions shares	Jan. 31, 2019 USD ($)	Jan. 31, 2018 USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future equity awards (in shares) | shares				74,571,031
Stock-based compensation expense				$ 226,705,000	$ 210,645,000	$ 150,673,000
Unrecognized compensation cost related to stock awards, weighted-average period				1 year 4 months 24 days
2015 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future equity awards (in shares) | shares				5,000,000
Dollar cap per purchase period		$ 7,500
Employee stock purchase plan offering period	24 months
Number of purchase periods | numberOfFinancialInstitutions				4
Purchase period, term				6 months
ESPP modification charge				$ 13,600,000		9,000,000.0
Stock-based compensation expense				24,500,000	$ 35,400,000	$ 18,300,000
Unrecognized stock-based compensation expense				$ 27,600,000
Unrecognized compensation cost related to stock awards, weighted-average period				1 year 7 months 6 days
Common stock | 2015 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future equity awards (in shares) | shares			3,500,000
Increase in shares reserved by percentage of capital stock			1.00%
Payroll deductions percentage			30.00%
Share cap for ESPP at purchase date (in shares) | shares			3,000
Calendar year gap for ESPP contribution amount			$ 25,000
Purchase price as percentage of fair market value of common stock			85.00%