Net Income 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		6 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 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)	293,909		149,390
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)	116,649		59,291
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)	153,751		78,150
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)	23,509		11,949
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)		155,692,789		154,916,528
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)		3,026,985		2,250,724