Note 12 - Fair Value Measurement (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

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

	Balance at December 31, 2019		Balance at December 31, 2018		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	62,452	$	27,389		Level 1
Available for sale securities:
Equity securities – mining industry		6,207		6,583		Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		11,952		4,184		Level 2
Derivative contracts:
Metal forward and put option contracts		—		209		Level 2
Foreign exchange contracts		1,184		23		Level 2
Restricted cash balances:
Certificates of deposit and other deposits		1,025		1,025		Level 1
Total assets	$	82,820	$	39,413
Liabilities
Derivative contracts:
Metal forward and put option contracts	$	5,777	$	373		Level 2
Foreign exchange contracts		1,437		8,595		Level 2
Total liabilities	$	7,214	$	8,968