Note 12 - Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2013

Fair Value Disclosures [Abstract]

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

	Balance at December 31, 2013		Balance at December 31, 2012		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	212,175	$	190,984	Level 1
Available for sale securities:
Equity securities – mining industry		7,019		9,614	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		17,672		17,555	Level 2
Derivative contracts:
Base metal forward contracts		4,461		5,606	Level 2
Restricted cash balances:
Certificates of deposit and other bank deposits		5,217		871	Level 1
Total assets	$	246,544	$	224,630
Liabilities:
Derivative contracts:
Base metal forward contracts	$	—	$	2,483	Level 2