Note 12 - Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2016

Notes Tables

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

	Balance at December 31, 2016		Balance at December 31, 2015		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	169,777	$	155,209	Level 1
Available for sale securities:
Debt securities – municipal and corporate bonds		29,117		—	Level 2
Equity securities – mining industry		5,002		1,515	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		20,082		13,490	Level 2
Derivative contracts:
Metal forward contracts		5,403		—	Level 2
Foreign exchange contracts		27		—	Level 2
Restricted cash balances:
Certificates of deposit and other bank deposits		2,200		999	Level 1
Total assets	$	231,608	$	171,213
Liabilities
Derivative contracts:
Metal forward contracts	$	192	$	—	Level 2
Foreign exchange contracts		5,288		—	Level 2
Total liabilities	$	5,480	$	—