BASIS OF PRESENTATION - Business Operations (Details)	0 Months Ended	9 Months Ended
	Apr. 28, 2014 mines	Sep. 30, 2014 mines
Canadian Acquisition
Business Acquisition [Line Items]
Number of mines	6	6
PMRU
Business Acquisition [Line Items]
Number of mines		5
Corporate Joint Venture | Canadian Acquisition
Business Acquisition [Line Items]
Ownership percentage in joint venture		50.00%
Corporate Joint Venture | PMRU
Business Acquisition [Line Items]
Ownership percentage in joint venture		50.00%