Note 12. Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2011

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Table Text Block]

	Balance at December 31, 2011		Balance at December 31, 2010		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	266,463	$	283,606	Level 1
Available for sale securities:
Equity securities – mining industry		3,923		2,668	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		10,996		36,295	Level 2
Derivative contracts:
Base metal forward contracts		32,750		—	Level 2
Restricted cash balances:
Certificates of deposit and other bank deposits		866		10,314	Level 1
Total assets	$	314,998	$	332,883
Liabilities:
Derivative contracts:
Base metal forward contracts	$	—	$	21,260	Level 2