COMMITTMENTS AND CONTINGENCIES: (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended	22 Months Ended
Dec. 31, 2011 person category	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Environmental costs
Environmental capital expenditure	$ 13.9	$ 13.9	$ 16.6	$ 27.5
Peru
Environmental costs
Environmental capital expenditure	2.4	2.4	6.4	2.4
Mexican Operations.
Environmental costs
Environmental capital expenditure	11.5	11.5	10.2	25.1
Number of categories of collective actions	3
Minimum number of people claiming injury due to collective action initiative in Civil Federal Procedures Code (CFPC)	30
Plant demolition and soil remediation budgeted cost		35.7
Plant demolition and soil cost recognized		$ 22.5

The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities.

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-Name Statement of Position (SOP)

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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+ Details