Note 11 - Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2021

Notes Tables

Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Table Text Block]

	Year Ended December 31,
	2021			2020			2019
Loss on derivative contracts	$	(32,655	)	$	(22,074	)	$	(3,971	)
Unrealized (loss) gain on investments in equity securities		(4,295	)		10,268			(2,389	)
Gain on disposition or exchange of investments		1,158			—			923
Total fair value adjustments, net	$	(35,792	)	$	(11,806	)	$	(5,437	)

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

	Balance at December 31, 2021		Balance at December 31, 2020		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	210,010	$	129,830	Level 1
Current and non-current investments:
Equity securities – mining industry		14,470		19,389	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		36,437		27,864	Level 2
Derivative contracts - other current assets and other non-current assets:
Metal forward and put option contracts		—		381	Level 2
Foreign exchange contracts		5,207		7,647	Level 2
Restricted cash balances:
Certificates of deposit and other deposits		1,053		1,053	Level 1
Total assets	$	267,177	$	186,164
Liabilities
Derivative contracts - current derivative liabilities and other non-current liabilities:
Metal forward and put option contracts	$	37,873	$	11,737	Level 2
Foreign exchange contracts		8		19	Level 2
Total liabilities	$	37,881	$	11,756