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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)
12 Months Ended
Dec. 31, 2017
Minimum  
Property, Plant and Equipment [Line Items]  
Useful life (in years) 3 years
Maximum  
Property, Plant and Equipment [Line Items]  
Useful life (in years) 15 years
Buildings  
Property, Plant and Equipment [Line Items]  
Useful life (in years) 15 years
Shop tools and equipment | Minimum  
Property, Plant and Equipment [Line Items]  
Useful life (in years) 3 years
Shop tools and equipment | Maximum  
Property, Plant and Equipment [Line Items]  
Useful life (in years) 5 years
Mining equipment  
Property, Plant and Equipment [Line Items]  
Useful life (in years) 5 years
Office equipment | Minimum  
Property, Plant and Equipment [Line Items]  
Useful life (in years) 4 years
Office equipment | Maximum  
Property, Plant and Equipment [Line Items]  
Useful life (in years) 5 years
Furniture and fixtures | Minimum  
Property, Plant and Equipment [Line Items]  
Useful life (in years) 5 years
Furniture and fixtures | Maximum  
Property, Plant and Equipment [Line Items]  
Useful life (in years) 7 years
Light trucks & utility vehicles  
Property, Plant and Equipment [Line Items]  
Useful life (in years) 5 years