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Stock-Based Compensation - Restricted Stock Units (RSUs) Activity (Detail) - Outstanding RSUs - $ / shares
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Number of Shares, Unvested, Beginning balance 1,140,964 875,589
Number of Shares, Granted 33,500 749,793
Number of Shares, Vested (649,872) (401,193)
Number of Shares, Forfeited/Canceled (57,750) (83,225)
Number of Shares, Unvested, Ending balance 466,842 1,140,964
Weighted-Average Grant Date Fair Value, Unvested, beginning balance $ 2.24 $ 6.70
Weighted-Average Grant Date Fair Value, Granted 6.43 1.12
Weighted-Average Grant Date Fair Value, Vested 2.05 8.82
Weighted-Average Grant Date Fair Value, Forfeited/Canceled 4.47 7.29
Weighted-Average Grant Date Fair Value, Unvested, ending balance $ 2.52 $ 2.24