Income Taxes - Reconciliation of Federal Income Tax Rate to Losses Before Income Tax Benefit (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income tax benefit at federal statutory rate	$ (6,379,000)	$ (6,140,000)
State income taxes, net of federal benefit	(582,000)	(570,000)
Non-deductible expenses	193,000	154,000
Federal rate impact	0	0
Research and development tax credits	(1,225,000)	(1,254,000)
Other	330,000	380,000
Change in valuation allowance	7,663,000	7,430,000
Total income tax provision	$ 0	$ 0