Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Treasury Stock	Convertible preferred stock
Temporary equity shares outstanding (in shares) at Jan. 31, 2016							43,594,000
Temporary equity, beginning of period at Jan. 31, 2016							$ 120,615
Temporary equity shares outstanding (in shares) at Jan. 31, 2017	43,594,753						43,594,000
Temporary equity, end of period at Jan. 31, 2017	$ 120,615						$ 120,615
Beginning of period (in shares) at Jan. 31, 2016		30,777,000
Beginning of period at Jan. 31, 2016	(95,236)	$ 37	$ 41,634	$ (1,267)	$ (123,735)	$ (11,905)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		618,000
Exercise of stock options	1,321	$ 1	1,320
Stock-based compensation	9,851		9,851
Other comprehensive income	(541)			(541)
Net loss	(43,150)				(43,150)
End of period (in shares) at Jan. 31, 2017		31,395,000
End of period at Jan. 31, 2017	$ (127,755)	$ 38	52,805	(1,808)	(166,885)	(11,905)
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of preferred stock (in shares)							(43,594,000)
Conversion of preferred stock							$ (120,615)
Temporary equity shares outstanding (in shares) at Apr. 30, 2017	0						0
Temporary equity, end of period at Apr. 30, 2017	$ 0						$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Initial public offering, net of issuance costs of $4,433 (in shares)		12,075,000
Initial public offering, net of issuance costs of $4,433	119,094	$ 12	119,082
Conversion of preferred stock (in shares)		43,594,000
Conversion of convertible preferred stock to common stock	120,615	$ 44	120,571
Conversion of preferred stock warrants to common stock warrants	$ 1,435		1,435
Exercise of stock options (in shares)	2,727,513	2,728,000
Exercise of stock options	$ 2,140	$ 3	2,137
Exercise of common stock warrants (in shares)		143,000
Exercise of common stock warrants	0
Vested restricted stock units converted to common shares (in shares)		60,000
Vested restricted stock units converted to common shares	0
Stock-based compensation	4,062		4,062
Other comprehensive income	192			192
Net loss	(16,106)				(16,106)
End of period (in shares) at Apr. 30, 2017		89,995,000
End of period at Apr. 30, 2017	103,677	$ 97	300,092	$ (1,616)	$ (182,991)	$ (11,905)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance costs	$ 1,969		$ 4,433