Note 15 - Acquisitions - Unaudited Pro Forma Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Mines Management [Member]
Sales of products	$ 645,957	$ 443,567
Net income (loss)	68,778	(89,806)
Income (loss) applicable to common shareholders	$ 68,226	$ (90,357)
Basic and diluted income (loss) per common share (in dollars per share)	$ 0.17	$ (0.24)
Revett Mining Company, Inc. [Member]
Sales of products		$ 445,703	$ 500,787
Net income (loss)		(89,118)	(44,099)
Income (loss) applicable to common shareholders		$ (89,670)	$ (44,651)
Basic and diluted income (loss) per common share (in dollars per share)		$ (0.24)	$ (0.12)