Organization and Description of Business - Initial Public Offering and Deferred Offering Costs (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	9 Months Ended
	Oct. 31, 2017	Oct. 31, 2017	Oct. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Proceeds from the IPO, net of underwriting discounts and commissions	$ 201,600
Underwriting discounts and commissions	15,500
Deferred offering costs	3,900
Redeemable convertible preferred stock outstanding (in shares)		41,233,452
Conversion of redeemable convertible preferred stock to common stock	$ 346,400	$ 346,428
Payment of offering costs		$ 2,344	$ 0
Common Stock
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Conversion of stock, shares converted (in shares)	26,952,887	26,953,404
Class A Common Stock | IPO
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of shares issued (in shares)	9,200,000
Stock price (in dollars per share)	$ 24	$ 24
Class A Common Stock | Over-Allotment Option
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of shares issued (in shares)	1,200,000
Redeemable Preferred Stock
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Redeemable convertible preferred stock outstanding (in shares)	41,232,762