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Summary of Activity for Stock Option Plans (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2021
Dec. 31, 2020
Stock Options Number Outstanding    
Beginning Balance 550,769  
Cancelled or Expired (292)  
Exercised (5,254)  
Ending Balance 545,223 550,769
Vested or expected to vest at March 31, 2021 545,223  
Exercisable at March 31, 2021 545,223  
Stock Options Average Exercise Price per share    
Beginning Balance $ 5.56  
Cancelled or Expired 14.40  
Exercised 6.50  
Ending Balance 5.53 $ 5.56
Vested or expected to vest at March 31, 2021 5.53  
Exercisable at March 31, 2021 $ 5.53  
Stock Options Remaining Contractual Life (in years)    
Weighted Average Remaining Contractual Term (Years) 4 years 8 months 4 days 4 years 10 months 17 days
Vested or expected to vest at March 31, 2021 4 years 8 months 4 days  
Exercisable at March 31, 2021 4 years 8 months 4 days  
Stock Options Aggregate Intrinsic Value    
Aggregate intrinsic value $ 3,318,621 $ 1,875,719
Vested or expected to vest at March 31, 2021 3,318,621  
Exercisable at March 31, 2021 $ 3,318,621