Contingencies (Details)	12 Months Ended
Dec. 31, 2015 processingFacility mine
Loss Contingencies [Line Items]
Loss contingency, number of processing facilities \| processingFacility	3
IDAHO
Loss Contingencies [Line Items]
Loss contingency, number of mines \| mine	18

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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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration