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Acquisitions - Additional Information (Detail)
$ in Millions
10 Months Ended 12 Months Ended
Dec. 31, 2020
USD ($)
Dec. 31, 2020
USD ($)
Mar. 10, 2020
Leagold Mining Corporation [member]      
Disclosure of detailed information about business combination [line items]      
Business combination profit loss as if combination occurred at the beginnig of the period   $ 1.0  
Leagold Mining Corporation [member]      
Disclosure of detailed information about business combination [line items]      
Percentage of voting interest acquired     100.00%
Business combination shares issued     0.331
Acquisition related costs $ 4.6    
Business combination total acquisition costs incurred 5.9    
Business combination revenue of acquiree since acquisition date 360.7    
Business combination revenue as if combination occurred at the beginnig of the period   $ 932.0  
Business combination profit loss of acquiree since acquisition date $ 24.3    
Business combination share exchange ratio     0.331