Note 13 - Fair Value Measurement (Tables)

9 Months Ended

Sep. 30, 2018

Notes Tables

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

Description	Balance at September 30, 2018		Balance at December 31, 2017		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	60,856	$	186,107	Level 1
Available for sale securities:
Debt securities - municipal and corporate bonds		—		33,758	Level 2
Equity securities – mining industry		7,190		7,561	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		12,947		14,805	Level 2
Restricted cash balances:
Certificates of deposit and other bank deposits		1,010		1,032	Level 1
Derivative contracts:
Foreign exchange contracts		1,760		4,943	Level 2
Metal forward contracts		282		—	Level 2
Total assets	$	84,045	$	248,206
Liabilities:
Derivative contracts:
Foreign exchange contracts	$	136	$	—	Level 2
Metal forward contracts		604		15,531	Level 2
Total liabilities	$	740	$	15,531