Leases - Additional Information (Detail)	1 Months Ended			12 Months Ended
	Sep. 30, 2020 USD ($)	Nov. 30, 2019 USD ($)	Jul. 31, 2019 USD ($) ft²	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Lessee Lease Description [Line Items]
Sublease income				$ 173,000
Future minimum commitment under non-cancelable operating lease				219,000
Operating lease right-of-use assets				398,000
Finance lease right-of-use assets				24,000
Current operating lease liabilities				305,000
Current finance lease liabilities				$ 17,000
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]				us-gaap:OtherLiabilitiesCurrent
Long-term operating lease liabilities				$ 139,000
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]				us-gaap:OtherLiabilitiesNoncurrent
Long-term finance lease liabilities				$ 8,000
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]				us-gaap:OtherLiabilitiesNoncurrent
Rent expense					$ 323,000
Sublease income					$ 277,000
Finance lease, weighted-average remaining lease term				1 year 4 months 24 days
Finance lease, discount rate				10.00%
Operating lease, weighted-average remaining lease term				1 year 4 months 24 days
Operating lease, discount rate				10.00%
Redwood City, California [Member]
Lessee Lease Description [Line Items]
Area of operating lease | ft²			6,368
Operating lease, description				the Company executed a non-cancellable lease agreement for 6,368 square feet of new space in Redwood City, California, which began in September 2019 and expires in May 2021.
Operating lease beginning date			2019-09
Operating lease, expiration			2021-05
Payment to acquire office furniture under operating lease			$ 1
Future minimum commitment under non-cancelable operating lease		$ 29,000
Redwood City, California [Member] | Forecast [Member]
Lessee Lease Description [Line Items]
Future minimum commitment under non-cancelable operating lease	$ 30,000
Capnia Inc Joint Venture [Member] | Redwood City, California [Member]
Lessee Lease Description [Line Items]
Sublease income				$ 65,000