Capital Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Class Of Stock [Line Items]
Conversion of preferred stock into common stock, value		$ 42,075
Reclassification of convertible preferred stock warrant liability into additional paid-in capital	$ 5,700	$ 5,711
Preferred stock, shares outstanding		0	0
Common stock, shares authorized		500,000,000	8,000,000
Common stock, par value		$ 0.005	$ 0.005
Common stock, shares issued		9,827,129	1,616,996
Common stock, shares outstanding		9,827,129	1,616,996
Common stock, voting rights		Holders of common stock have voting rights equal to one vote per share of common stock held
Preferred stock, shares authorized		20,000,000	20,000,000
Preferred stock, par value		$ 0.005	$ 0.005
Preferred stock, shares issued		0	0
Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares outstanding		0
Common Stock
Class Of Stock [Line Items]
Conversion of preferred stock into common stock, shares	4,689,753	4,689,753
Conversion of preferred stock into common stock, value		$ 23
Additional Paid-in Capital
Class Of Stock [Line Items]
Conversion of preferred stock into common stock, value		42,052
Reclassification of convertible preferred stock warrant liability into additional paid-in capital	$ 42,100	$ 42,100