Property, Plant, Equipment and Mineral Interests (Details Textual)	9 Months Ended
Sep. 30, 2017
Property, Plant and Equipment [Line Items]
Description of Mining Equipment	the Company acquired 4 pieces of mining equipment (2016 1) from Komatsu through financing agreements and disposed of 2 pieces of mining equipment (2016 nil).

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration