CoSense Joint Venture Agreement and Discontinued Operations - Additional Information (Detail)		1 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended
	Oct. 16, 2018 shares	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) $ / shares
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Current period gain recognized			$ 2,000,000
Minority interest investment in former subsidiary			978,000				$ 978,000
Loss from minority interest investment						$ (478,000)	(160,000)
Gain in minority interest investment		$ 33,000,000
Loss from discontinued operations							(1,494,000)
Stock-based compensation expense						825,000	1,300,000
Discontinued Operations, Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Stock-based compensation expense						0	76,000
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]
Assets held for sale, current			0			0	0
Assets held for sale, long-term			0			0	0
Liabilities held for sale, current			0			0	0
Liabilities held for sale, long-term			$ 0			0	0
Loss from discontinued operations						$ 0	$ (1,494,000)
Sinon Investments LLC [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total purchase price		$ 500,000,000
Capnia Inc Joint Venture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Negotiated price per share | $ / shares				$ 1.00
Percentage of ownership interest				47.00%
Number of shares owned | shares				1,480,000
Percentage of discount for lack of control				0.23
Loss from minority interest investment					$ 511,000,000
Capnia Inc Joint Venture [Member] | Sinon Investments LLC [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of ownership interest		47.00%
Minority interest investment in former subsidiary		$ 467,000,000			467,000,000
OAHL [Member] | Capnia Inc Joint Venture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Minority interest investment in former subsidiary		$ 0			$ 0
OAHL [Member] | Capnia Inc Joint Venture [Member] | Corporate Joint Venture [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Investment threshold requirement								$ 2,200,000
Negotiated price per share | $ / shares								$ 1.00
Investment threshold requirement stock issuance				$ 1,200,000				$ 1,200,000
Issuance of common stock (shares) | shares	1,690,322
Percentage of ownership interest	53.00%