CoSense Joint Venture Agreement and Discontinued Operations - Components of Income of Discontinued Operations (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Expenses
Net loss from discontinued operations		$ (1,494,000)
CoSense, NFI and Serenz [Member] | Discontinued Operations, Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Product revenue		62,000
Cost of product revenue		32,000
Gross profit		30,000
Expenses
Research and development		1,106,000
Sales and marketing		25,000
General and administrative		393,000
Total expenses		1,524,000
Operating loss		(1,494,000)
Net loss from discontinued operations	$ 0	$ (1,494,000)