Note 16 - Acquisitions - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net (loss) income			$ 68,778
(Loss) income applicable to common shareholders			$ 68,226
Basic and diluted (loss) income per common share (in dollars per share)			$ 0.17
Klondex Mines Ltd [Member]
Sales	$ 680,261	$ 785,859	$ 834,789
Net (loss) income	(19,574)	(35,203)	73,724
(Loss) income applicable to common shareholders	$ (20,126)	$ (35,755)	$ 73,172
Basic and diluted (loss) income per common share (in dollars per share)	$ (0.04)	$ (0.08)	$ 0.16
Revett Mining Company, Inc. [Member]
Sales			$ 645,957