Nature of Business (Details) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended
	Oct. 04, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Initial Public Offering
Common stock authorized shares	100,000,000	100,000,000		100,000,000
Shares of common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001		$ 0.0001
Shares of undesignated preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001		$ 0.0001
Shares of undesignated preferred stock, authorized	10,000,000	10,000,000		10,000,000
Common stock warrants
Initial Public Offering
Number of shares issuable upon net exercise of outstanding warrants	463,589
Common Stock
Initial Public Offering
Redesignation of Class A and Class B common stock upon initial public offering (in shares)	5,583,405
Conversion of redeemable convertible preferred stock upon initial public offering (in shares)	5,089,436
Shares issued upon exercise of warrants (in shares)	202,061	28,431	210,817
IPO
Initial Public Offering
Issuance of common stock upon public offering (in shares)	4,300,000
Issuance price (in dollars per share)	$ 12.00
Proceeds from issuance of common stock under initial public offering, net of underwriting costs	$ 55,186
Underwriting discounts and commissions	$ 4,154
Underwriter option
Initial Public Offering
Issuance of common stock upon public offering (in shares)	645,000