Note 13 - Acquisitions - Unaudited Proforma Financial Information (Details) - Mines Management [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Sales of products	$ 179,393	$ 104,941	$ 481,712	$ 328,230
Net income (loss)	26,322	(10,934)	47,988	(27,799)
Income (loss) applicable to common shareholders	$ 26,184	$ (11,071)	$ 47,574	$ (28,213)
Basic and diluted income (loss) per common share (in dollars per share)	$ 0.07	$ (0.03)	$ 0.12	$ (0.07)