Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Line Items]
Tax benefit recognized			$ 0
AMT credit carryforwards			736,000
Provisional tax benefit due to new Tax Act			122,000
Untaxed accumulated unremitted foreign earnings			813,000
Valuation allowance, deferred tax assets	$ 30,363,000	$ 30,031,000
Research and development tax credit carryforwards	27,607,000	23,244,000
Accrued interest	2,070,000	1,462,000	1,104,000	$ 946,000
Net interest expense	7,000	7,000	$ 6,000
Potential payment of interest	$ 41,000	$ 35,000
Minimum [Member]
Income Tax Disclosure [Line Items]
Effective income tax rate		21.00%
Maximum [Member]
Income Tax Disclosure [Line Items]
Effective income tax rate			35.00%
Domestic Tax Authority [Member]
Income Tax Disclosure [Line Items]
Federal net operating loss carryforwards expiry, beginning year			2025
Research and development tax credit carryforwards			$ 14,451,000
Certain States [Member]
Income Tax Disclosure [Line Items]
Federal net operating loss carryforwards expiry, beginning year			2022
Federal net operating loss carryforwards expiry, ending year			2037
Research and development tax credit carryforwards			$ 17,744,000
Net operating loss carryforwards			$ 4,913,000