Property and Equipment, Net - Schedule of Property and Equipment Net (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 1,341	$ 839
Less: Accumulated depreciation and amortization	(487)	(240)
Property and equipment, net	854	599
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	651	221
Furniture and Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	209	202
Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	111	102
Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	99	44
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 271	$ 270