Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Oct. 31, 2017	Oct. 31, 2017	Apr. 30, 2013
Class of Warrant or Right [Line Items]
Exercise of common stock warrants (in shares)		85,170
Redeemable convertible preferred stock		$ 1,171
Warrants outstanding (in shares)	0	0
Series E and Series F Redeemable Convertible Preferred Stock
Class of Warrant or Right [Line Items]
Exercise price (in dollars per share)	$ 0.01	$ 0.01
Class B Common Stock | Financial Institution 1
Class of Warrant or Right [Line Items]
Exercise price (in dollars per share)			$ 5.72
Number of shares convertible from warrant exercise (in shares)			116,258
Class B Common Stock | Financial Institution 2
Class of Warrant or Right [Line Items]
Exercise price (in dollars per share)			$ 5.72
Number of shares convertible from warrant exercise (in shares)			5,785
Warrant
Class of Warrant or Right [Line Items]
Warrants outstanding (in shares)	0	0
Common Stock
Class of Warrant or Right [Line Items]
Exercise of common stock warrants (in shares)		99,534
Series E and Series F Redeemable Convertible Preferred Stock
Class of Warrant or Right [Line Items]
Redeemable convertible preferred stock		$ 1,200
Series E Redeemable Convertible Preferred Stock
Class of Warrant or Right [Line Items]
Exercise of common stock warrants (in shares)		45,301
Series F Redeemable Convertible Preferred Stock
Class of Warrant or Right [Line Items]
Exercise of common stock warrants (in shares)		41,258
Class B Common Stock | Common Stock
Class of Warrant or Right [Line Items]
Exercise of common stock warrants (in shares)	53,562	99,534