Note 13 - Acquisition of Klondex (Details Textual) $ / shares in Units, $ in Thousands			3 Months Ended	37 Months Ended
	Jul. 20, 2018 USD ($) $ / shares shares	Jul. 19, 2018 shares	Mar. 31, 2019 USD ($) shares	Mar. 31, 2019 shares	Dec. 31, 2018 shares
Common Stock, Shares, Issued, Total | shares			482,987,752	482,987,752	482,603,937
Stock Issued During Period, Shares, New Issues | shares			0	7,173,614
Common Stock, Shares, Outstanding, Ending Balance | shares			482,987,752	482,987,752	482,603,937
Warrants in Connection with Klondex Mines Acquisition [Member]
Class of Warrant or Right, Issued During Period | shares	4,136,000
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right | shares	1
Warrants in Connection with Klondex Mines Acquisition Expiring April 2032 [Member]
Class of Warrant or Right, Outstanding | shares	2,068,000
Warrants in Connection with Klondex Mines Acquisition Expiring February 2029 [Member]
Class of Warrant or Right, Outstanding | shares	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 | shares	182,048,945	180,499,319
Stock Issued During Period, Shares, New Issues | shares		1,549,626
Common Stock, Shares, Outstanding, Ending Balance | shares	182,048,945	180,499,319
Klondex Mines Ltd [Member]
Business Acquisition, Share Price | $ / shares	$ 2.27
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 | shares	75,276,176
Stock Issued During Period, Shares, New Issues | shares	75,276,176
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares	$ 8.02
Share-based Payment Arrangement, Cash Used to Settle Award	$ 2,000
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	242,389
Business Combination, Consideration Transferred, Total	413,923
Business Combination, Subscrition of New Formed Company, Value	7,000
Business Combination, Settlement of Certain Equity Compensation Value	1,500
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Inventory			$ 200
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment			8,700
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Noncurrent Deferred Tax Liability			9,100
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Accounts Payable and Accrued Liabilities			$ 500
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Mineral Interest	220,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Depletable Mineral Interest	46,000
Klondex Mines Ltd [Member] | Hecla Warrants [Member]
Class of Warrant or Right, Issued During Period, Value	9,800
Klondex Mines Ltd [Member] | Maximum [Member]
Payments to Acquire Businesses, Gross	$ 153,200
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares	75,276,176