Stockholders' Equity - Summary of Stock Based Compensation Expense (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock compensation expense	$ 175,000	$ 199,000	$ 377,000	$ 558,000
Continuing Operations [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock compensation expense	175,000	179,000	377,000	519,000
Research and Development [Member] | Continuing Operations [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock compensation expense	49,000	34,000	102,000	139,000
General and Administrative [Member] | Continuing Operations [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock compensation expense	$ 126,000	$ 145,000	$ 275,000	$ 380,000