Note 12. Fair Value Measurement (Detail) - Assets And Liabilities Accounted For At Fair Value (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Trade accounts receivable:
Receivables from provisional concentrate sales	$ 9,313	$ 545
Restricted cash balances:
Total assets	314,998	332,883
Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents:
Money market funds and other bank deposits	266,463	283,606
Available for sale securities:
Equity securities – mining industry	3,923	2,668
Restricted cash balances:
Certificates of deposit and other bank deposits	866	10,314
Fair Value, Inputs, Level 2 [Member]
Trade accounts receivable:
Receivables from provisional concentrate sales	10,996	36,295
Derivative contracts:
Base metal forward contracts	32,750
Derivative contracts:
Base metal forward contracts		$ 21,260

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