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Related Parties - Changes of Number of Shares Granted (Detail) - shares
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Related parties details 3 [abstract]    
Share granted, beginning 1,224,524 1,700,128
Cancellation of granted shares due to termination of executive employment (200,000)  
Shares vested and transferred (322,264) (475,604)
Share granted, ending 702,260 1,224,524