Net Loss Per Share - Schedule of Outstanding Shares of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	13,455,145	333,308
Series A Warrants For Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	7,802,241
Series B Warrants For Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	2,574,727
Stock options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	2,351,055	331,469
Warrants for Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total potential dilutive shares	727,122	1,839