Preferred Stock, Common Stock and Stockholders' Equity - Summary of Nonvested Options Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value Per Share, Granted	$ 0.91	$ 1.86
2007 Plan and 2013 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Options Nonvested, Outstanding beginning balance	1,117,407
Options, Granted	2,672,246
Options Vested	(494,674)
Options, Expired/Forfeited/Exchanged	(1,411,213)
Options Nonvested, Outstanding ending balance	1,883,766	1,117,407
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value Per Share, Nonvested beginning balance	$ 2.44
Weighted Average Grant Date Fair Value Per Share, Granted	1.20
Weighted Average Grant Date Fair Value Per Share, Vested	1.53
Weighted Average Grant Date Fair Value Per Share, Nonvested ending balance	$ 0.75	$ 2.44