Warrant Liabilities - Additional Information (Detail) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 19, 2018 $ / shares shares	Dec. 15, 2017 $ / shares shares
Class Of Warrant Or Right [Line Items]
Change in fair value of stock warrants	$ 689	$ (7,116)	$ (6,532)	$ (930)
Expected Dividend Yield [Member]
Class Of Warrant Or Right [Line Items]
Measurement input	0.00		0.00
Series C Warrant [Member]
Class Of Warrant Or Right [Line Items]
Warrant liability	$ 0		$ 0
2017 PIPE Warrant Liability [Member]
Class Of Warrant Or Right [Line Items]
Warrant liability	4,777		$ 4,777		$ 10,822
Number of warrants issued to purchase common stock | shares							8,141,116
Warrant to call common stock | shares							0.74
Exercise price of warrants exercised | $ / shares							$ 2.00
Warrant issuance description			The 2017 PIPE Warrants were issued on December 15, 2017 in the 2017 PIPE Offering, pursuant to a Warrant Agreement with each of the investors in the 2017 PIPE Offering, and entitle the holder of each of the 8,141,116 units to purchase 0.74 shares of the Company’s common stock at an exercise price equal to $2.00 per share, subject to adjustment as discussed below, at any time commencing upon issuance of the 2017 PIPE Warrants and terminating on December 15, 2020.
Change in fair value of stock warrants	500		$ (6,000)
Fair value of estimated warrants	$ 4,800		$ 4,800
2017 PIPE Warrant Liability [Member] | Minimum [Member]
Class Of Warrant Or Right [Line Items]
Exercise price of warrants exercised | $ / shares	$ 1.72		$ 1.72
2018 PIPE Warrant Liability [Member]
Class Of Warrant Or Right [Line Items]
Warrant liability	$ 867		$ 867		$ 1,354
Number of warrants issued to purchase common stock | shares						10,272,375
Warrant to call common stock | shares						0.05
Exercise price of warrants exercised | $ / shares						$ 2.00
Warrant issuance description			The 2018 PIPE Warrants were issued on December 19, 2018 in the 2018 PIPE Offering, pursuant to a Warrant Agreement with each of the investors in the 2018 PIPE Offering, and entitle the holders of each of the 10,272,375 units to purchase 0.05 shares of the Company’s common stock at an exercise price equal to $2.00 per share, subject to adjustment as discussed below, at any time commencing upon issuance of the 2018 PIPE Warrants and terminating on December 21, 2023.
Change in fair value of stock warrants	100		$ (500)
Fair value of estimated warrants	$ 900		$ 900
2018 PIPE Warrant Liability [Member] | Minimum [Member]
Class Of Warrant Or Right [Line Items]
Exercise price of warrants exercised | $ / shares	$ 2.00		$ 2.00