Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Total property and equipment	$ 430	$ 406
Less: accumulated depreciation	(112)	(85)
Property and equipment, net	318	321
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	68	65
Machinery and Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	38	38
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	210	194
Computers
Property Plant And Equipment [Line Items]
Total property and equipment	81	76
Office Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	11	11
Software
Property Plant And Equipment [Line Items]
Total property and equipment	$ 22	$ 22