Note 12 - Fair Value Measurement (Detail) - Assets And Liabilities Accounted For At Fair Value (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Trade accounts receivable:
Receivables from provisional concentrate sales	$ 7,466	$ 9,313
Restricted cash balances:
Total assets	224,630	314,998
Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents:
Money market funds and other bank deposits	190,984	266,463
Available for sale securities:
Equity securities – mining industry	9,614	3,923
Restricted cash balances:
Certificates of deposit and other bank deposits	871	866
Fair Value, Inputs, Level 2 [Member]
Trade accounts receivable:
Receivables from provisional concentrate sales	17,555	10,996
Derivative contracts:
Base metal forward contracts	5,606	32,750
Derivative contracts:
Base metal forward contracts	$ 2,483

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