Annual report pursuant to Section 13 and 15(d)

Fair Value of Warrants - Summary of Derivative Warrant Activity (Detail)

v3.21.1
Fair Value of Warrants - Summary of Derivative Warrant Activity (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Class of Warrants Outstanding [Roll Forward]    
Beginning balance $ 178 $ 248
Fair value of warrants exchanged for stock   (10)
Change in fair value of warrants (167) (70)
Ending balance 1 178
2016 Offerings    
Class of Warrants Outstanding [Roll Forward]    
Beginning balance 178 225
Fair value of warrants exchanged for stock   (10)
Change in fair value of warrants (167) (47)
Ending balance 1 178
2017 Offerings    
Class of Warrants Outstanding [Roll Forward]    
Beginning balance 0 23
Fair value of warrants exchanged for stock   0
Change in fair value of warrants 0 (23)
Ending balance $ 0 $ 0