Note 12 - Fair Value Measurement (Tables)

9 Months Ended

Sep. 30, 2016

Notes Tables

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

Description	Balance at September 30, 2016		Balance at December 31, 2015		Input Hierarchy Level
Assets:
Cash and cash equivalents:
Money market funds and other bank deposits	$	167,844	$	155,209	Level 1
Available for sale securities:
Debt securities - municipal and corporate bonds		24,534		—	Level 2
Equity securities – mining industry		6,356		1,515	Level 1
Trade accounts receivable:
Receivables from provisional concentrate sales		26,622		13,490	Level 2
Restricted cash balances:
Certificates of deposit and other bank deposits		6,084		999	Level 1
Derivative contracts:
Foreign exchange contracts		48		—	Level 2
Total assets	$	231,488	$	171,213
Liabilities:
Derivative contracts:
Foreign exchange contracts	$	1,604	$	—	Level 2
Metal forward contracts		1,004		283	Level 2
Total liabilities	$	2,608	$	283