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STOCK-BASED COMPENSATION - Summary of RSU Activity (Detail) - RSU - $ / shares
3 Months Ended
Mar. 31, 2021
Mar. 31, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]    
Unvested at December 31, 2020, Number of Shares 8,046,399  
RSUs granted, Number of Shares 2,890,478  
RSUs vested, Number of Shares (1,556,823)  
RSUs forfeited, Number of Shares (162,558)  
Unvested at March 31, 2021, Number of Shares 9,217,496  
Vested and unreleased, Number of Shares 177,644  
Outstanding at March 31, 2021, Number of Shares 9,395,140  
Unvested at December 31, 2020, Weighted Average Grant Date Fair Value $ 3.41  
RSUs granted, Weighted Average Grant Date Fair Value 4.67 $ 3.09
RSUs vested, Weighted Average Grant Date Fair Value 3.54  
RSUs forfeited, Weighted Average Grant Date Fair Value 3.66  
Unvested at March 31, 2021, Weighted Average Grant Date Fair Value $ 3.79