BASIS OF PRESENTATION - Sherritt Acquisition (Details) (USD $)	3 Months Ended		0 Months Ended	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 24, 2013 Sherritt International Corporation [Member] mines	Mar. 31, 2014 Sherritt International Corporation [Member]
Business Acquisition [Line Items]
Number of Mines			7
Business Acquisition, Percentage of Voting Interests Acquired			50.00%
Business Combination, Consideration Transferred			$ 435,000,000
Payments to Acquire Businesses, Gross			293,000,000
Business Combination, Consideration Transferred, Liabilities Incurred			142,000,000
Business Combination, Acquisition Related Costs				18,100,000
Loss on foreign exchange	(6,790,000)	0		6,800,000
Interest Expense, Debt				6,100,000
Interest Expense	20,798,000	10,160,000		4,900,000
Other Expenses				$ 300,000