Summary of Significant Accounting Policies - Summary of Property, Plant and Equipment (Detail) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 190,000
Less accumulated depreciation	(17,000)
Total	173,000	$ 0
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	173,000
Software
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 17,000