Note 10 - Fair Value Measurement (Tables)

9 Months Ended

Sep. 30, 2021

Notes Tables

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

Description	Balance at September 30, 2021		Balance at December 31, 2020		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	190,904	$	129,830	Level 1
Current and non-current investments:
Equity securities		8,030		19,389	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		32,821		27,864	Level 2
Restricted cash balances:
Certificates of deposit and other deposits		1,053		1,053	Level 1
Derivative contracts - current and non-current derivative assets:
Foreign exchange contracts		4,655		7,647	Level 2
Metal forward and put option contracts		7,313		381	Level 2
Total assets	$	244,776	$	186,164
Liabilities:
Derivative contracts - current derivatives liabilities and other non-current liabilities:
Foreign exchange contracts	$	200	$	19	Level 2
Metal forward and put option contracts		4,731		11,737	Level 2
Total liabilities	$	4,931	$	11,756