Fair Value Measurements - Schedule of Changes in Series B Redeemable Convertible Preferred Stock Warrant Fair Value (Details) - Redeemable Convertible Preferred Stock Warrant - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance as of beginning of period	$ 304	$ 237
Increase in fair value of warrant	104	67
Reclassification of remaining warrant liability to additional paid-in capital	(408)
Balance as of end of period	$ 0	$ 304