BUSINESS SEGMENTS (Mine Production and Purchase Percentages) (Details)	12 Months Ended
	Dec. 31, 2011
Mining Segment Reporting Information [Line Items]
Percentage of Atlantic Copper's annual concentrate requirements purchased from PT Freeport Indonesia (in hundredths)	17.00%
Percentage of Atlantic Copper's annual concentrate requirements purchased from FCX's South America mines (in hundredths)	30.00%
Mines Individually Classified As Reportable Segments [Member] | Morenci [Member]
Mining Segment Reporting Information [Line Items]
Percentage of Division's Copper Production (in hundredths)	42.00%
Mines Individually Classified As Reportable Segments [Member] | Cerro Verde [Member]
Mining Segment Reporting Information [Line Items]
Percentage of Division's Copper Production (in hundredths)	50.00%