Equity - Summary of Stock-Based Compensation Expense (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized expense at March 31, 2019	$ 44,000
Weighted average remaining years to vest	7 months 28 days
Research and Development Expenses [Member] | Stock Based Compensation [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expenses	$ 46,000	$ 20,000	$ 77,000	$ 73,000
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expenses	255,000	95,000	415,000	347,000
General and Administrative Expenses [Member] | Common Stock Issued for Services [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expenses	0	0	60,000	60,000
General and Administrative Expenses [Member] | Stock Based Compensation [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expenses	$ 209,000	$ 75,000	$ 278,000	$ 214,000