Fair Value Measurements - Schedule of Reconciliation of Redeemable Convertible Preferred Stock Warrant Liability (Details) - Redeemable Convertible Preferred Stock Warrant Liability $ in Thousands	9 Months Ended
	Oct. 31, 2017 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	$ 1,272
Issuance of redeemable convertible preferred stock warrants	0
Conversion of redeemable convertible preferred stock warrant liability into redeemable convertible preferred stock	(1,171)
Change in fair value of redeemable convertible preferred stock warrant liability	(101)
Fair value, ending balance	$ 0