Property, Plant and Equipment - Schedule of Property, Plant and Equipment, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 1,880	$ 275
Accumulated depreciation	(58)	(20)
Total property, plant and equipment, net	1,822	255
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	68	68
Office Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	48	48
Office Equipment [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	28	28
Construction in Progress [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 1,736	$ 131