Note 4 - Business Segments, Sales of Products and Significant Customers - Sales by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Sales by geographical area	$ 808,016	$ 708,253	$ 674,549
Sales by significant product type	808,016	708,253	674,549
Doré and Metals from Doré [Member]
Sales by geographical area	313,337	266,536	340,912
Sales by significant product type	313,337	266,536	340,912
Carbon [Member]
Sales by geographical area	4,117	60,302	37,645
Sales by significant product type	4,117	60,302	37,645
Silver Concentrate [Member]
Sales by geographical area	345,732	281,050	200,456
Sales by significant product type	345,732	281,050	200,456
Zinc Concentrate [Member]
Sales by geographical area	112,448	76,481	74,160
Sales by significant product type	112,448	76,481	74,160
Precious Metals Concentrate [Member]
Sales by geographical area	32,382	23,884	21,376
Sales by significant product type	32,382	23,884	21,376
UNITED STATES
Sales by geographical area	71,278	115,378	53,612
Sales by significant product type	71,278	115,378	53,612
CANADA
Sales by geographical area	419,090	321,896	379,095
Sales by significant product type	419,090	321,896	379,095
JAPAN
Sales by geographical area	63,588	39,418	48,841
Sales by significant product type	63,588	39,418	48,841
NETHERLANDS
Sales by geographical area	0	(923)	38,420
Sales by significant product type	0	(923)	38,420
KOREA, REPUBLIC OF
Sales by geographical area	203,115	166,402	154,581
Sales by significant product type	203,115	166,402	154,581
CHINA
Sales by geographical area	50,945	66,082	0
Sales by significant product type	$ 50,945	$ 66,082	$ 0