Note 12 - Fair Value Measurement (Tables)

3 Months Ended

Mar. 31, 2014

Fair Value Disclosures [Abstract]

Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Table Text Block]

Description	Balance at March 31, 2014		Balance at December 31, 2013		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	207,642	$	212,175	Level 1
Available for sale securities:
Equity securities – mining industry		8,730		7,019	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		26,159		17,672	Level 2
Restricted cash balances:
Certificates of deposit and other bank deposits		7,702		5,217	Level 1
Derivative contracts:
Metal forward contracts		13,308		4,461	Level 2
Total assets	$	263,541	$	246,544