Net Income (Loss) Per Share Attributable to Common Stockholders - Summary of Potential Shares of Common Stock Excluded from Computation of Diluted Net Income Per Share Attributable to Common Stockholders (Details) - shares	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Class A Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	652,938		504,483
Issuance of common stock reserved for charitable donation (in shares)			500,000
Class A Common Stock | Outstanding stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	219,660		113,335
Class A Common Stock | Unvested RSUs
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	369,894		361,923
Class A Common Stock | Purchase rights committed under the ESPP
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	63,384		29,225
Class B Common Stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)		188,065,864		155,916,214
Class B Common Stock | Convertible preferred stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)		152,665,804		152,665,804
Class B Common Stock | Outstanding stock options
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)		34,222,303		3,250,410
Class B Common Stock | Shares subject to repurchase from early exercised stock options and restricted stock
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)		1,177,757		0