CoSense Joint Venture Agreement and Discontinued Operations - Additional Information (Detail) - Capnia Inc Joint Venture [Member] - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended
	Oct. 16, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of ownership interest		47.00%	47.00%
OAHL [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Remaining interest		$ 0
OAHL [Member] | Corporate Joint Venture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Investment threshold requirement				$ 2,200
Negotiated price per share				$ 1.00
Investment threshold requirement stock issuance			$ 1,200	$ 1,200
Sale of common stock in public offering, net of costs, (shares)	1,690,322
Percentage of ownership interest	53.00%