Note 9 - Fair Value Measurement (Tables)

6 Months Ended

Jun. 30, 2021

Notes Tables

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

Description	Balance at June 30, 2021		Balance at December 31, 2020		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	181,494	$	129,830	Level 1
Current and non-current investments
Equity securities		11,083		19,389	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		41,311		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 derivatives assets:
Foreign exchange contracts		10,341		7,647	Level 2
Metal forward and put option contracts		389		381	Level 2
Total assets	$	245,671	$	186,164
Liabilities:
Derivative contracts - current derivatives liabilities and other non-current liabilities:
Foreign exchange contracts	$	—	$	19	Level 2
Metal forward and put option contracts		13,860		11,737	Level 2
Total liabilities	$	13,860	$	11,756