Net Loss Per Share - Potentially Dilutive Securities Not Included in the Diluted Per Share Calculations (Details) - shares shares in Thousands	3 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the diluted per share calculation	17,871	16,673
Issued and outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the diluted per share calculation	12,577	13,357
Unvested RSUs and restricted stock issued and outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the diluted per share calculation	4,994	2,969
Shares committed under ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the diluted per share calculation	300	347