Note 9 - Fair Value Measurement (Tables)

3 Months Ended

Mar. 31, 2021

Notes Tables

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

Description	Balance at March 31, 2021		Balance at December 31, 2020		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	139,750	$	129,830	Level 1
Current and non-current investments:
Equity securities – mining industry		11,717		19,389	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		35,274		27,864	Level 2
Restricted cash balances:
Certificates of deposit and other bank deposits		1,053		1,053	Level 1
Derivative contracts - current and non-current derivatives assets:
Metal forward and put option contracts		4,349		381	Level 2
Foreign exchange contracts		9,192		7,647	Level 2
Total assets	$	201,335	$	186,164
Liabilities:
Derivative contracts - current derivatives liabilities and other non-current liabilities:
Metal forward and put option contracts	$	4,742	$	11,737	Level 2
Foreign exchange contracts		—		19	Level 2
Total Liabilities	$	4,742	$	11,756