Net Loss per Share Attributable to Common Stockholders - Schedule of Antidilutive Securities Excluded from the Computation of Diluted Net loss per share (Details) - shares	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Redeemable Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	24,316,192	25,853,450	26,045,352	25,853,450
Warrants Subject to Mandatory Redemption
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	1,339	54,604	30,122	54,604
Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	116,485	122,043	120,190	122,043
Employee Stock Option | 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)	9,321,627	11,220,176	9,783,945	10,736,027
Employee Stock Option | 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)	3,258,405	0	2,207,524	0
Early Exercised Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	318,240	117,487	236,231	67,528