Note 12 - Fair Value Measurement (Tables)

3 Months Ended

Mar. 31, 2015

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

Description	Balance at March 31, 2015		Balance at December 31, 2014		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	196,231	$	209,665	Level 1
Available for sale securities:
Equity securities – mining industry		4,334		4,920	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		27,280		17,696	Level 2
Restricted cash balances:
Certificates of deposit and other bank deposits		883		883	Level 1
Derivative contracts:
Metal forward contracts		14,317		11,347	Level 2
Total assets	$	243,045	$	244,511