Note 12 - Fair Value Measurement (Details) - Assets And Liabilities Accounted For At Fair Value (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Trade accounts receivable:
Receivables from provisional concentrate sales	$ 20,228	$ 7,466
Derivative contracts:
Total assets	343,385	224,630
Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents:
Money market funds and other bank deposits	296,375	190,984
Available for sale securities:
Equity securities – mining industry	8,766	9,614
Restricted cash balances:
Certificates of deposit and other bank deposits	5,287	871
Fair Value, Inputs, Level 2 [Member]
Trade accounts receivable:
Receivables from provisional concentrate sales	8,306	17,555
Derivative contracts:
Base metal forward contracts	24,651	5,606
Derivative contracts:
Base metal forward contracts		$ 2,483