Description of Business and Basis of Presentation - Reverse Stock Split, Initial Public Offering and Going Concern (Details) $ / shares in Units, $ in Thousands				12 Months Ended
	Aug. 30, 2018 USD ($) $ / shares shares	Aug. 16, 2018 USD ($) $ / shares shares	Aug. 03, 2018 shares	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Description of Business and Basis of Presentation
Proceeds from issuance of common stock, net				$ 25,079
Working capital				23,100
Accumulated deficit				$ (71,088)	$ (47,626)
IPO
Description of Business and Basis of Presentation
Proceeds from issuance of common stock, gross	$ 2,500	$ 26,000
Proceeds from issuance of common stock, net	2,300	22,800
Underwriting discounts and commissions	$ 200	1,800
Other offering expenses		$ 1,400
Common Stock
Description of Business and Basis of Presentation
Ratio of reverse stock split			0.155814
Conversion of Series A convertible preferred stock into common stock upon initial public offering (in shares) | shares			5,744,586
Common Stock | IPO
Description of Business and Basis of Presentation
Issuance of stock (in shares) | shares	192,824	2,000,000
Offering price per share | $ / shares	$ 13.00	$ 13.00