Significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2019

Significant Accounting Policies [Abstract]

Disclosure of detailed information about estimated useful life or depreciation rate [Table Text Block]

Asset Class	Estimated Useful Life
Fixed plant & related components and infrastructure	Units of production over life of mine
Mobile and other mine equipment components	3 to 12 years
Computer equipment and software	3 years
Right-of-use assets	Straight-line over lease term