Note 12 - Fair Value Measurement (Tables)

6 Months Ended

12 Months Ended

Jun. 30, 2013

Dec. 31, 2012

Fair Value Disclosures [Abstract]

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

Description	Balance at June 30, 2013		Balance at December 31, 2012		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	296,375	$	190,984	Level 1
Available for sale securities:
Equity securities – mining industry		8,766		9,614	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		8,306		17,555	Level 2
Restricted cash balances:
Certificates of deposit and other bank deposits		5,287		871	Level 1
Derivative contracts:
Base metal forward contracts		24,651		5,606	Level 2
Total assets	$	343,385	$	224,630
Liabilities:
Derivative contracts:
Base metal forward contracts		—		2,483	Level 2

	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