Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Contingency [Line Items]
Increase (decrease) in valuation allowance	$ 3.8	$ 4,300,000
Total gross deferred tax assets	15,727,000	13,207,000
Unrecognized tax benefits	39,000	$ 39,000	$ 72,000
Federal [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards	52,300,000
Net operating loss carryforwards not subject to expiration	47,500,000
Net operating loss carryforwards subject to expire	$ 4,800,000
Operating loss carryforwards, expiration	Begin to expire in 2037
Federal [Member] | Research and Development Tax Credits [Member]
Income Tax Contingency [Line Items]
Tax credits	$ 90,000
Tax credit, expiration	Begin to expire in 2037