Note 12 - Fair Value Measurement (Tables)

3 Months Ended

Mar. 31, 2020

Notes Tables

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

Description	Balance at March 31, 2020		Balance at December 31, 2019		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	215,715	$	62,452	Level 1
Equity securities:
Equity securities – mining industry		4,919		6,207	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		6,062		11,952	Level 2
Restricted cash balances:
Certificates of deposit and other bank deposits		1,053		1,025	Level 1
Derivative contracts:
Metal forward and put option contracts		8,811		—	Level 2
Foreign exchange contracts		—		1,184	Level 2
Total assets	$	236,560	$	82,820
Liabilities:
Derivative contracts:
Metal forward and put option contracts	$	69	$	5,777	Level 2
Foreign exchange contracts		19,471		1,437	Level 2
Total Liabilities	$	19,540	$	7,214