Net Loss Per Share - Schedule of Antidilutive Securities Excluded from the Computation of Diluted Net Loss per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2020	Jul. 31, 2019
Stock options to purchase common stock | Class A Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,421,627	2,212,684	1,534,260	2,342,061
Stock options to purchase common stock | Class B Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	4,097,316	5,185,198	4,212,209	5,442,820
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	4,038,134	2,926,998	3,952,552	2,744,235
Early exercised stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	6,346	31,583	8,231	39,480
Shares underlying the conversion spread in the convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	889,896	2,409,899	798,754	2,177,490