Nature of Business (Details) - USD ($) $ / shares in Units, $ in Thousands			9 Months Ended	12 Months Ended
	Oct. 12, 2016	Oct. 04, 2016	Oct. 03, 2016	Dec. 31, 2016	Dec. 31, 2015
Initial Public Offering
Proceeds from issuance of common stock under initial public offering, net of underwriting costs				$ 55,186
Common stock authorized shares		100,000,000		100,000,000	27,836,869
Shares of common 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
Shares of undesignated preferred stock, par value (in dollars per share)		$ 0.0001		$ 0.0001	$ 0.0001
Common stock warrants
Initial Public Offering
Number of shares issuable upon net exercise of outstanding warrants		463,589	232,787
Common Stock
Initial Public Offering
Issuance of common stock upon public offering (in shares)				4,945,000
Redesignation of Class A and Class B common stock upon initial public offering (in shares)		5,583,405		5,583,405
Conversion of redeemable convertible preferred stock upon initial public offering (in shares)		5,089,436		5,089,436
Shares issued upon exercise of warrants (in shares)	288,324	202,061	210,817	490,385
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