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FINANCIAL INSTRUMENTS AND RISK MANAGEMENT - Commodity price sensitivity and hedging (Details)
R in Millions
Dec. 31, 2019
oz
Dec. 31, 2019
R / oz
Dec. 31, 2019
R / kg
Dec. 31, 2019
ZAR (R)
Oct. 21, 2019
oz
Oct. 21, 2019
kg
Oct. 21, 2019
R / oz
Oct. 21, 2019
R / kg
Apr. 11, 2019
oz
Apr. 11, 2019
kg
Apr. 11, 2019
$ / oz
Dec. 31, 2018
ZAR (R)
Dec. 31, 2017
ZAR (R)
Foreign currency sensitivity analysis                          
Amount of hedged instrument         67,856 2,111     105,906 3,294      
Average Price             17,371 558,491          
Contracts amount | R       R 3,836.2               R 6,317.3 R 5,626.0
Minimum                          
Foreign currency sensitivity analysis                          
Average Price | $ / oz                     1,200    
Maximum                          
Foreign currency sensitivity analysis                          
Average Price | $ / oz                     1,323    
Forward contract | Minimum                          
Foreign currency sensitivity analysis                          
Average Price   19,222 618,001                    
Forward contract | Maximum                          
Foreign currency sensitivity analysis                          
Average Price   21,218 682,174                    
Forward contract | Commodity price risk                          
Foreign currency sensitivity analysis                          
Amount of hedged instrument | oz 88,415                        
Futures contract | Commodity price risk                          
Foreign currency sensitivity analysis                          
Contracts amount | R       R 0.0               R 0.0 R 0.0