Supplementary cash flow information - Non-cash investing and financing activities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Statement Of Cash Flows [Line Items]
Interest on loan to non-controlling interest	$ 203
Share-based payments, capitalized to mineral property interests	2,507	$ 3,622
Change in current liabilities relating to mineral property expenditures	(14,277)	(6,759)
Foreign exchange gains (losses)	4,065	(1,012)
Interest expense, capitalized to mineral property interests	0	20,052
Shares issued for purchase of non-controlling interest	0	(2,000)
Fekola Equipment Loan Facility
Statement Of Cash Flows [Line Items]
Foreign exchange gains (losses)	3,312	(4,776)
Fekola SA
Statement Of Cash Flows [Line Items]
Non-controlling interest sold in exchange for loan receivable (Note 8)	47,000	0
Kronk
Statement Of Cash Flows [Line Items]
Restricted cash and cash equivalents	1,000
Deficit
Statement Of Cash Flows [Line Items]
Interest on loan to non-controlling interest	$ 1,352	$ 0

Capital Expenditures Incurred But Not Yet Paid1

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Interest Income On Loan Receivable To Noncontrolling Interest

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Issue Of Equity, Purchase Of Non-controlling Interest

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Noncash Transaction, Non-controlling Interest Sold In Exchange For Loan Receivable

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Share-based Payments Capitalized

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[Line Items] for Statement Of Cash Flows [Table]

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The amount of exchange differences recognised in profit or loss that arise from foreign currency transactions, excluding those arising on financial instruments measured at fair value through profit or loss in accordance with IFRS 9. [Refer: At fair value [member]; Financial instruments, class [member]]

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The amount of interest costs that an entity incurs in connection with the borrowing of funds that are directly attributable to the acquisition, construction or production of a qualifying asset and which form part of the cost of that asset.

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