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Note 12 - Fair Value Measurement (Details) - Assets And Liabilities Accounted For At Fair Value (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2013
Dec. 31, 2012
Trade accounts receivable:    
Receivables from provisional concentrate sales $ 17,263 $ 7,466
Restricted cash balances:    
Total assets 304,771 224,630
Fair Value, Inputs, Level 1 [Member]
   
Cash and cash equivalents:    
Money market funds and other bank deposits 237,836 190,984
Available for sale securities:    
Equity securities – mining industry 8,364 9,614
Restricted cash balances:    
Certificates of deposit and other bank deposits 5,378 871
Fair Value, Inputs, Level 2 [Member]
   
Trade accounts receivable:    
Receivables from provisional concentrate sales 34,481 17,555
Restricted cash balances:    
Base metal forward contracts 18,712 5,606
Base metal forward contracts   $ 2,483