Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Total property and equipment	$ 379	$ 44
Less: accumulated depreciation	(60)	(5)
Property and equipment, net	319	39
Machinery and Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	38	38
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	65
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	176
Computers
Property Plant And Equipment [Line Items]
Total property and equipment	69	$ 6
Office Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	9
Software
Property Plant And Equipment [Line Items]
Total property and equipment	$ 22