Note 13 - Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2020

Notes Tables

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

	Balance at December 31, 2020		Balance at December 31, 2019		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	129,830	$	62,452	Level 1
Current and non-current investments:
Equity securities – mining industry		19,389		6,207	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		27,864		11,952	Level 2
Derivative contracts - other current assets and other non-current assets:
Metal forward and put option contracts		381		—	Level 2
Foreign exchange contracts		7,647		1,184	Level 2
Restricted cash balances:
Certificates of deposit and other deposits		1,053		1,025	Level 1
Total assets	$	186,164	$	82,820
Liabilities
Derivative contracts - current derivative liabilities and other non-current liabilities:
Metal forward and put option contracts	$	11,737	$	5,777	Level 2
Foreign exchange contracts		19		1,437	Level 2
Total liabilities	$	11,756	$	7,214