Note 12 - Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2012

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

	Balance at December 31, 2012		Balance at December 31, 2011		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	190,984	$	266,463	Level 1
Available for sale securities:
Equity securities – mining industry		9,614		3,923	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		17,555		10,996	Level 2
Derivative contracts:
Base metal forward contracts		5,606		32,750	Level 2
Restricted cash balances:
Certificates of deposit and other bank deposits		871		866	Level 1
Total assets	$	224,630	$	314,998
Liabilities:
Derivative contracts:
Base metal forward contracts	$	2,483	$	—	Level 2