Note 14 - Acquisition of Klondex Mines Ltd. (Details Textual) $ / shares in Units, $ in Thousands			9 Months Ended	31 Months Ended
	Jul. 20, 2018 USD ($) $ / shares shares	Jul. 19, 2018 shares	Sep. 30, 2018 USD ($) shares	Sep. 30, 2018 shares	Dec. 31, 2017 shares	Sep. 30, 2017 shares
Common Stock, Shares, Issued, Total			479,909,466	479,909,466	399,176,425
Stock Issued During Period, Shares, New Issues			1,025,911	5,634,758
Common Stock, Shares, Outstanding, Ending Balance			479,909,466	479,909,466	399,176,425
Class of Warrant or Right, Outstanding						0
Warrants in Connection with Klondex Mines Acquisition [Member]
Class of Warrant or Right, Issued During Period	4,136,000
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right	1
Warrants in Connection with Klondex Mines Acquisition Expiring April 2032 [Member]
Class of Warrant or Right, Outstanding	2,068,000
Warrants in Connection with Klondex Mines Acquisition Expiring February 2029 [Member]
Class of Warrant or Right, Outstanding	2,068,000
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares	$ 1.57
Klondex Mines Ltd [Member]
Common Stock, Shares, Issued, Total	182,048,945	180,499,319
Stock Issued During Period, Shares, New Issues		1,549,626
Common Stock, Shares, Outstanding, Ending Balance	182,048,945
Klondex Mines Ltd [Member]
Business Acquisition, Share Price | $ / shares	$ 2.24
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
Business Combination, Consideration, Cash Alternative, Price Per Share | $ / shares	$ 2.47
Business Combination, Consideration, Share Alternative, Share Exchange Rate	0.6272
Business Combination Consideration, Combined Alternative, Price Per Share | $ / shares	$ 0.8411
Business Combination Consideration, Combined Alternative, Share Exchange Rate	0.4136
Payments to Acquire Businesses, Gross | $	$ 161,704
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	75,276,176
Stock Issued During Period, Shares, New Issues	75,276,176
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares	$ 8.02
Employee Service Share-based Compensation, Cash Flow Effect, Cash Used to Settle Awards | $	$ 2,000
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable | $	242,389
Business Combination, Consideration Transferred, Total | $	414,248
Business Combination, Subscrition of New Formed Company, Value | $	7,000
Business Combination, Settlement of Certain Equity Compensation Value | $	1,500
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual | $			$ 11,500
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual | $			$ (10,100)
Klondex Mines Ltd [Member] | Hecla Warrants [Member]
Class of Warrant or Right, Issued During Period, Value | $	10,200
Klondex Mines Ltd [Member] | Maximum [Member]
Payments to Acquire Businesses, Gross | $	$ 153,200
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	75,276,176