Fair Value Measurements - Schedule of Changes in Series B Redeemable Convertible Preferred Stock Warrant Fair Value (Details) - Redeemable Convertible Preferred Stock Warrant $ in Thousands	6 Months Ended
	Jul. 31, 2017 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance as of beginning of period	$ 304
Increase in fair value of warrant through exercise date	103
Reclassification of remaining warrant liability to additional paid-in capital	(407)
Balance as of end of period	$ 0