Note 12 - Fair Value Measurement (Details) - Assets and Liabilities Accounted for at Fair Value (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Trade accounts receivable:
Receivables from provisional concentrate sales	$ 10,650	$ 20,893
Derivative contracts:
Total assets	263,541	246,544
Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents:
Money market funds and other bank deposits	207,642	212,175
Available for sale securities:
Equity securities – mining industry	8,730	7,019
Restricted cash balances:
Certificates of deposit and other bank deposits	7,702	5,217
Fair Value, Inputs, Level 2 [Member]
Trade accounts receivable:
Receivables from provisional concentrate sales	26,159	17,672
Derivative contracts:
Metal forward contracts	$ 13,308	$ 4,461