DERIVATIVE INSTRUMENTS (Details) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014
Not Designated as Hedging Instrument | Foreign Exchange Forward
Derivative [Line Items]
Number of foreign currency exchange forward contracts	2	2
Notional amount	$ 348,300,000	$ 348,300,000
Not Designated as Hedging Instrument | Foreign Exchange Forward | Gain (loss) on foreign exchange
Derivative [Line Items]
Gain (loss) on derivative, net	0	(6,209,000)
Not Designated as Hedging Instrument | Power Contract [Member] | Derivative loss [Member]
Derivative [Line Items]
Gain (loss) on derivative, net	(23,691,000)	(29,621,000)
Not Designated as Hedging Instrument | Power Contract [Member] | Other current liabilities
Derivative [Line Items]
Derivative Liability	4,206,000	4,206,000
Not Designated as Hedging Instrument | Power Contract [Member] | Other liabilities
Derivative [Line Items]
Derivative Liability	$ 25,415,000	$ 25,415,000
Minimum | Power Contract [Member]
Derivative [Line Items]
Contracted power price notional amount		41.05
Maximum | Power Contract [Member]
Derivative [Line Items]
Contracted power price notional amount		56.33
Weighted Average [Member] | Power Contract [Member]
Derivative [Line Items]
Contracted power price notional amount		43.73