Overview and Basis of Presentation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Apr. 07, 2017	Apr. 06, 2017	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Class of Stock [Line Items]
Initial public offering costs			$ 4,038	$ 1,584	$ 0
Class A Common Stock
Class of Stock [Line Items]
Price per share in initial public offering (in dollars per share)	$ 17.00
Common stock outstanding (in shares)			70,609,898	0
Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Redeemable convertible preferred stock converted to common class B stock (in shares)		59,491,640
Class B Common Stock
Class of Stock [Line Items]
Common class B stock after conversion of redeemable convertible stock (in shares)		59,491,640
Common stock outstanding (in shares)			33,361,106	20,229,000
Initial Public Offering
Class of Stock [Line Items]
Proceeds from initial public offering, net of underwriters' discounts and commissions	$ 200,000
Initial public offering costs	$ 5,600
Initial Public Offering | Class A Common Stock
Class of Stock [Line Items]
Shares issued in initial public offering (in shares)	12,650,000
Underwriters' Option to Purchase Additional Shares | Class A Common Stock
Class of Stock [Line Items]
Shares issued in initial public offering (in shares)	1,650,000