SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Details 3) (USD $)	3 Months Ended	12 Months Ended			3 Months Ended
	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Correction to interest rate for capitalized interest
SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)
Increase in property, plant and equipment		$ 1,529,570,000	$ 1,181,320,000		$ 10,000,000
Depreciation, depletion and amortization		832,293,000	793,200,000		1,200,000
Decrease to interest expense		28,684,000	21,954,000	30,062,000	11,200,000
Decrease to interest expense for prior years					9,400,000
Impairment recorded related to the carrying value of assets at the Pontiki mine	$ 19,000,000	$ 19,031,000