Net Loss Per Share - Potentially Dilutive Securities (Details) - shares shares in Thousands	6 Months Ended
	Jul. 31, 2020	Jul. 31, 2019
Potentially dilutive securities
Antidilutive securities excluded from computation of earnings per share, amount	15,443	13,015
Shares subject to outstanding common stock options
Potentially dilutive securities
Antidilutive securities excluded from computation of earnings per share, amount	504	326
Shares subject to outstanding RSUs, PSUs and RSAs
Potentially dilutive securities
Antidilutive securities excluded from computation of earnings per share, amount	12,450	12,347
Employee stock purchase plan
Potentially dilutive securities
Antidilutive securities excluded from computation of earnings per share, amount	341	342
Shares underlying the conversion spread in the convertible senior notes
Potentially dilutive securities
Antidilutive securities excluded from computation of earnings per share, amount	2,148	0