Income and Mining Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Beginning unrecognized tax benefits	$ 5,324	$ 7,157
Gross increase to current period tax positions	0	202
Gross increase to prior period tax positions	37	316
Reductions in unrecognized tax benefits resulting from a lapse of the applicable statute of limitations	(1,585)	(2,351)
Ending unrecognized tax benefits	$ 3,776	$ 5,324

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Amount of unrecognized tax benefits.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

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