Note 12 - Fair Value Measurement (Tables)

6 Months Ended

Jun. 30, 2017

Notes Tables

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

Description	Balance at June 30, 2017		Balance at December 31, 2016		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	164,113	$	169,777	Level 1
Available for sale securities:
Debt securities - municipal and corporate bonds		37,816		29,117	Level 2
Equity securities – mining industry		4,729		5,002	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		9,183		20,082	Level 2
Restricted cash balances:
Certificates of deposit and other deposits		1,098		2,200	Level 1
Derivative contracts:
Foreign exchange contracts		2,286		27	Level 2
Metal forward contracts		1,208		5,403	Level 2
Total assets	$	220,433	$	231,608
Liabilities:
Derivative contracts:
Foreign exchange contracts	$	585	$	5,288	Level 2
Metal forward contracts		1,383		192	Level 2
Total Liabilities	$	1,968	$	5,480