Convertible Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	Jul. 31, 2017	Jun. 30, 2017	Apr. 30, 2017	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Temporary Equity [Line Items]
Series E and E-1 Convertible Preferred Stock purchase price			$ 43.47828
Series E and E-1 Convertible Preferred Stock threshold of stock price trigger			$ 47.826108
Deemed dividend to Series E and E-1 Convertible Preferred Stock			$ 6,600	$ (6,588)
Conversion of convertible preferred stock		7,382,007
Number of common stock purchase		1,666,665
Warrant exercisable period		10 years
Warrant exercised price		$ 16.44
Gain on extinguishment				26,300
Common stock warrants issued to Series E-2 and F-2 Holders				$ 14,641	$ 0	$ 0
Warrants exercisable upon additional loan drawn				34,058
Additional loan drawn				$ 50,000
Facility Agreement
Temporary Equity [Line Items]
Additional loan drawn				$ 10,000
Common Stock
Temporary Equity [Line Items]
Conversion of convertible preferred stock				17,992,973
Convertible Preferred Stock Warrants
Temporary Equity [Line Items]
Conversion of convertible preferred stock				68,633
Common Stock Warrants
Temporary Equity [Line Items]
Conversion of stock				205,897
Warrants exercisable upon additional loan drawn				34,058
IPO
Temporary Equity [Line Items]
Proceeds from issuance of common stock			$ 50,000
IPO | Common Stock
Temporary Equity [Line Items]
Conversion of convertible preferred stock	17,992,973			17,992,973