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Derivative Financial Instruments and Fair Value and Credit Risk of Financial Instruments - Additional information (Detail) (USD $)
In Millions, unless otherwise specified
 1 Months Ended 12 Months Ended
Jun. 30, 2013
bbl
Dec. 31, 2013
bbl
Dec. 31, 2012
Dec. 31, 2011
Unionized Employees Concentration Risk [Member]
        
Derivative [Line Items]        
Unionized workforce participation   74.00%    
Unionized Employees Concentration Risk [Member] | Peru
        
Derivative [Line Items]        
Unionized workforce participation   14.00%    
Unionized Employees Concentration Risk [Member] | Australia
        
Derivative [Line Items]        
Unionized workforce participation   0.00%    
Unionized Employees Concentration Risk [Member] | South Africa
        
Derivative [Line Items]        
Unionized workforce participation   91.00%    
Unionized Employees Concentration Risk [Member] | Ghana
        
Derivative [Line Items]        
Unionized workforce participation   95.00%    
Commodity Contract
        
Derivative [Line Items]        
LME copper prices, average price per ton   7,324 7,951 8,836
LME copper prices, average provisional price (per ton)   6,575    
Applicable forward copper price   7,142    
Commodity cash settle and swap transaction, volume 7,500      
Derivative contracts, price per barrel 115.00      
Commodity cash settle and swap transaction outstanding, volume   30,000    
Commodity cash settle and swap transaction, mark-to-market value   $ 0.3    
Commodity Contract | Sales
        
Derivative [Line Items]        
Gain (loss) on mark-to-market value of contracts   $ (7.9) $ 15.6 $ (20.6)