XML 38 R40.htm IDEA: XBRL DOCUMENT v2.4.0.6
INCOME TAXES: (Details 2) (USD $)
In Millions, unless otherwise specified
 9 Months Ended
Sep. 30, 2012
Minimum
  
Income Taxes  
Reasonably possible increase in unrecognized tax benefit during the next 12 months $ 30
Maximum
  
Income Taxes  
Reasonably possible increase in unrecognized tax benefit during the next 12 months 50
Peru
  
Income Taxes  
Operating income margin (as a percent) 10.00%
Increase in special mining tax rate for each 5% increase up to 85% increase in operating income margin (as a percent) 0.40%
Provision for special mining tax $ 40.5
Peru | Minimum
  
Income Taxes  
Special mining tax (as a percent) 2.00%
Increment in operating income margin (as a percent) 5.00%
Peru | Maximum
  
Income Taxes  
Special mining tax (as a percent) 8.40%
Increment in operating income margin (as a percent) 85.00%