Capital Stock - Schedule of Common Stock Reserved for Future Issuance (Details) - shares		Dec. 31, 2017	Dec. 31, 2016
Class Of Stock [Line Items]
Common stock reserved for future issuance		2,813,593	6,890,085
Warrants to Purchase Common Stock
Class Of Stock [Line Items]
Common stock reserved for future issuance		468,278
Options Outstanding
Class Of Stock [Line Items]
Common stock reserved for future issuance		1,294,128	1,130,141
Shares Available for Future Grant
Class Of Stock [Line Items]
Common stock reserved for future issuance		1,003,875	390,164
Unvested Restricted Stock Units
Class Of Stock [Line Items]
Common stock reserved for future issuance		47,312
Series B-1 Convertible Preferred Stock Warrants
Class Of Stock [Line Items]
Common stock reserved for future issuance			680,027
Series B-1 Convertible Preferred Stock
Class Of Stock [Line Items]
Common stock reserved for future issuance			3,848,023
Series A-2 Convertible Preferred Stock
Class Of Stock [Line Items]
Common stock reserved for future issuance	[1]		841,730
Convertible Preferred Stock and Warrants
Class Of Stock [Line Items]
Common stock reserved for future issuance			5,369,780

[1] Reflects the effect of an amendment and restatement of the Company’s amended and restated certificate of incorporation in March 2017 to implement a conversion feature for the Series A-2 convertible preferred stock.