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Goodwill (Tables)
 12 Months Ended
Dec. 31, 2019
Intangible assets and goodwill [abstract]  
Disclosure of detailed information about key assumptions for the CGU's [Table Text Block]
    2019     2018  
Long-term gold price (per ounce)   US$1,400     US$1,300  
Long-term silver price (per ounce)   US$18     US$18  
Post-tax real discount rate   4.1%     5.1%