Equity Incentive Plans - 2015 Employee Stock Purchase Plan (Details)	1 Months Ended	12 Months Ended
	Feb. 28, 2019 USD ($)	Jan. 31, 2021 USD ($) financialInstitution shares	Feb. 02, 2020 USD ($) shares	Jan. 31, 2019 USD ($)	Jan. 31, 2016 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for future equity awards (in shares) | shares		67,368,912
Stock-based compensation expense		$ 242,344,000	$ 226,705,000	$ 210,645,000
Unrecognized compensation cost related to stock awards, weighted-average period		2 years 2 months 12 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
Employee stock purchase plan offering period		24 months
Number of purchase periods | financialInstitution		4
Purchase period, term		6 months
ESPP modification charge		$ 23,800,000	13,600,000	0
Stock-based compensation expense		25,800,000	$ 24,500,000	$ 35,400,000
Unrecognized stock-based compensation expense		$ 32,800,000
Unrecognized compensation cost related to stock awards, weighted-average period		1 year 2 months 12 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
Dollar cap per purchase period	$ 7,500
Purchase price as percentage of fair market value of common stock		85.00%