XML 75 R44.htm IDEA: XBRL DOCUMENT v3.8.0.1
Summary of significant accounting policies (Property, plant and equipment) (Details)
 12 Months Ended
Dec. 31, 2017
Mining interests [Member]  
Disclosure of detailed information about property, plant and equipment [line items]  
Estimated useful live of plant and equipment unit of production based upon estimated proven and probable reserves
Plant and equipment [Member]  
Disclosure of detailed information about property, plant and equipment [line items]  
Estimated useful live of plant and equipment 3 – 30 years over straight line basis
Corporate Office equipment [Member]  
Disclosure of detailed information about property, plant and equipment [line items]  
Estimated useful live of plant and equipment 3 – 10 years over straight line basis