Dilutive Shares Which Could Exist Pursuant to Exercise of Outstanding Stock Instruments and Which were not Included in Calculation (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive shares not included in calculation	16,053,050	17,664,953
Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive shares not included in calculation	12,538,204	10,647,026
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive shares not included in calculation	3,000,256	2,713,979
Contingently Issuable Shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive shares not included in calculation	514,590	4,303,948