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Stock-Based Compensation - Summary of Stock Option Activity (Detail) - 2006 and 2014 Stock Option Plans and Inducement Plan [Member] - Stock Options [Member] - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Dec. 31, 2020
Dec. 31, 2021
Share-Based Compensation        
Number of Shares Outstanding, beginning of the period 9,868,947      
Number of Shares, Granted 578,500      
Number of Shares, Exercised 0 (42,626)    
Number of Shares, Forfeited (81,466)      
Number of Shares, Cancelled (426,205)      
Number of Shares Outstanding, end of the period 9,939,776      
Number of Shares, Exercisable 5,688,369      
Number of Shares, Vested or expected to vest 9,321,200      
Weighted-Average Exercise Price Per Share Outstanding, beginning of the period $ 2.88      
Weighted-Average Exercise Price Per Share, Granted 0.41      
Weighted-Average Exercise Price Per Share, Forfeited 1.01      
Weighted-Average Exercise Price Per Share, Cancelled 2.29      
Weighted-Average Exercise Price Per Share Outstanding, end of the period 2.77      
Weighted-Average Exercise Price Per Share, Exercisable 4.07      
Weighted-Average Exercise Price Per Share, Vested or expected to vest $ 2.89      
Weighted-Average Remaining Contractual Term, Outstanding 7 years 3 months   7 years 1 month 2 days  
Weighted-Average Remaining Contractual Term, Exercisable 6 years 1 month 28 days      
Weighted-Average Remaining Contractual Term, Vested or expected to vest 7 years 1 month 20 days      
Aggregate Intrinsic Value, Outstanding $ 118     $ 51
Aggregate Intrinsic Value, Exercisable 28      
Aggregate Intrinsic Value, Vested or expected to vest $ 102