Description of Operations and Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended
	Sep. 30, 2016	Sep. 30, 2017	Dec. 31, 2016
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit		$ (219,055)	$ (200,324)
Common Class B Converted From Common Stock Warrants
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Conversion ratio	100.00%
Warrants outstanding	47,893
Common Class B Converted From Common
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Conversion ratio	100.00%
Common Class B Converted From Convertible Preferred Stock Warrant
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Conversion ratio	100.00%
Warrants outstanding	27,321
Convertible Preferred Stock
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Conversion of preferred stock to Class B common stock, Shares	18,239,475
IPO | Class A Common Stock
Description Of Operations And Summary Of Significant Accounting Policies [Line Items]
Shares sold (in shares)	6,900,000
Share price (in dollars per share)	$ 16.00
Net proceeds after deducting underwriting discounts and commissions and offering expenses	$ 99,000