Property and Equipment - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 548	$ 548
Less accumulated depreciation	(437)	(416)
Total	111	132
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	384	384
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 164	$ 164