CoSense Joint Venture Agreement and Discontinued Operations - Additional Information (Detail)		3 Months Ended
	Oct. 16, 2018 shares	Mar. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 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
Loss from discontinued operations				$ (514,000)
Stock-based compensation expense		$ 202,000		359,000
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		19,000
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
Assets held for sale, long-term		0	0
Liabilities held for sale, current		0	0
Liabilities held for sale, long-term		0	$ 0
Loss from discontinued operations		$ 0		$ (514,000)
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
Drcrease in minority interest investment		$ (190,000)
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	$ 1,200,000
Issuance of common stock (shares) | shares	1,690,322
Percentage of ownership interest	53.00%