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ACQUISITIONS AND DIVESTITURES - Acquisition of Acacia (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended 12 Months Ended
Jan. 01, 2020
Sep. 17, 2019
Dec. 31, 2020
Sep. 30, 2020
Dec. 31, 2019
Sep. 30, 2020
Dec. 31, 2020
Disclosure of detailed information about business combination [line items]              
Proportion of ownership interests held by non-controlling interests 16.00%            
Proportion of ownership interest in subsidiary             100.00%
Government of Tanzania              
Disclosure of detailed information about business combination [line items]              
Proportion of ownership interests held by non-controlling interests             16.00%
Acacia Mining PLC              
Disclosure of detailed information about business combination [line items]              
Proportion of ownership interests held by non-controlling interests   36.10%          
Share for share exchange   0.168          
Number of shares issued   24,836,670          
Proportion of interest held by shareholders   1.00%          
Increase (decrease) through change in equity of subsidiaries, equity       $ 70      
Proportion of ownership interest in subsidiary     100.00%   100.00% 63.90% 84.00%