Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 198	$ 370	$ 495
Proceeds from sale of property and equipment			41
Shelton Operating Lease [Member]
Property, Plant and Equipment [Line Items]
Write-off of fully-depreciated Shelton property and equipment			7,816
Proceeds from sale of property and equipment			$ 41