Stockholders’ Equity and Equity Incentive Plans - Additional Information (Details)		1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 31, 2020 USD ($) $ / shares shares	Apr. 30, 2019 USD ($) shares	Jul. 31, 2020 USD ($) $ / shares shares	Jul. 31, 2019 shares	Jul. 31, 2020 USD ($) $ / shares shares	Jul. 31, 2019 shares	Jan. 31, 2020 USD ($) $ / shares shares	Apr. 30, 2020 dates
Class of Stock [Line Items]
Common stock, par value (in dollars per share) | $ / shares	$ 0.001		$ 0.001		$ 0.001		$ 0.001
Stock options outstanding (in shares)	11,869,518		11,869,518		11,869,518		16,833,009
Unrecognized stock-based compensation expenses related to outstanding unvested stock options | $	$ 61,500,000		$ 61,500,000		$ 61,500,000
Number of offering dates | dates								4
Proceeds from unvested shares of common stock | $					900,000		$ 1,200,000
RSUs
Class of Stock [Line Items]
Unrecognized stock-based compensation excepted to be recognized over a weighted-average period	3 years
Unrecognized stock-based compensation expenses | $	$ 619,300,000		619,300,000		$ 619,300,000
Shares vested on the grant date (in shares)					166,366
Employee Stock Purchase Plan
Class of Stock [Line Items]
Unrecognized stock-based compensation excepted to be recognized over a weighted-average period	10 months 24 days
Unrecognized stock-based compensation expenses | $	$ 56,000,000.0		$ 56,000,000.0		$ 56,000,000.0
Maximum number of shares per employee (in shares)		3,000
Consecutive offering period		27 months
Share-based Payment Arrangement, Option
Class of Stock [Line Items]
Unrecognized stock-based compensation excepted to be recognized over a weighted-average period					2 years 3 months 18 days
2011 Plan
Class of Stock [Line Items]
Number of shares available for future issuance (in shares)	24,300,889		24,300,889		24,300,889
2019 Plan
Class of Stock [Line Items]
Percentage of shares reserved increase	5.00%		5.00%		5.00%
2019 Employee Stock Purchase Plan | Employee Stock Purchase Plan
Class of Stock [Line Items]
Annual increase in shares for available for future issuance by percentage of the outstanding ordinary shares on the first day of such fiscal year.		1.00%
Annual increase in Number of shares of common stock available for future issuance		7,500,000
Class A Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	2,000,000,000		2,000,000,000		2,000,000,000		2,000,000,000
Common stock, capital shares reserved for future issuance, charitable donation (in shares)	94,844					500,000
Antidilutive securities excluded from computation of earnings per share, amount	405,156		121,592	293,909	616,924	149,390
Class A Common Stock | Held For Charitable Contributions
Class of Stock [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount			23,300,000
Class A Common Stock | Employee Stock Purchase Plan
Class of Stock [Line Items]
Percentage of purchase price of common stock to fair market value of common stock on offering or purchase date		85.00%
ESPP excess rate purchase right, value | $		$ 25,000
Shares issued of common stock (in shares)					1,096,192
Class A Common Stock | 2019 Plan
Class of Stock [Line Items]
Number of shares available for future issuance (in shares)	58,300,889		58,300,889		58,300,889
Numbers of additional shares authorized under the plan (in shares)					34,000,000
Class A Common Stock | 2019 Employee Stock Purchase Plan | Employee Stock Purchase Plan
Class of Stock [Line Items]
Number of shares available for future issuance (in shares)		9,000,000
Class A Common Stock | Initial public offering
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	2,000,000,000		2,000,000,000		2,000,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.001		$ 0.001		$ 0.001
Class B Common Stock
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	300,000,000		300,000,000		300,000,000		300,000,000
Number of common stock subject to repurchase (in shares)					354,087		466,819
Weighted average price per share (in dollars per share) | $ / shares	$ 2.65		$ 2.65		$ 2.65		$ 2.58
Antidilutive securities excluded from computation of earnings per share, amount			0	0		0
Class B Common Stock | Initial public offering
Class of Stock [Line Items]
Common stock, shares authorized (in shares)	300,000,000		300,000,000		300,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.001		$ 0.001		$ 0.001