Note 13 - Subsequent Events (Details Textual)				1 Months Ended	6 Months Ended	28 Months Ended
		Jul. 20, 2018 USD ($) $ / shares shares	Jul. 19, 2018 shares	Aug. 08, 2018 USD ($)	Jun. 30, 2018 USD ($) shares	Jun. 30, 2018 USD ($) shares	Jan. 01, 2020	Sep. 30, 2018	Jul. 16, 2018 USD ($)	Jul. 15, 2018 USD ($)	Dec. 31, 2017 shares	May 31, 2016 USD ($)
Common Stock, Shares, Issued, Total | shares					401,322,377	401,322,377					399,176,425
Stock Issued During Period, Shares, New Issues | shares					0	4,608,847
Letters of Credit Outstanding, Amount					$ 3,000,000	$ 3,000,000
Common Stock, Shares, Outstanding, Ending Balance | shares					401,322,377	401,322,377					399,176,425
Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity												$ 100,000,000
Revolving Credit Facility [Member] | Scenario, Forecast [Member]
Leverage Ratio							4	4.5
Letter of Credit [Member]
Letter of Credit Outstanding, Fronting Fee												0.20%
Maximum [Member]
Leverage Ratio					4	4
Maximum [Member] | Letter of Credit [Member]
Letter of Credit, Participation Fee, Percent												3.25%
Minimum [Member] | Letter of Credit [Member]
Letter of Credit, Participation Fee, Percent												2.25%
Subsequent Event [Member]
Letters of Credit Outstanding, Amount				$ 3,000,000
Subsequent Event [Member] | Revolving Credit Facility [Member]
Line of Credit Facility, Current Borrowing Capacity									$ 200,000,000
Line of Credit Facility, Maximum Borrowing Capacity									$ 250,000,000	$ 100,000,000
Proceeds from Lines of Credit, Total				$ 47
Subsequent Event [Member] | Letter of Credit [Member]
Letter of Credit Outstanding, Fronting Fee									0.20%
Subsequent Event [Member] | 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
Subsequent Event [Member] | Warrants in Connection with Klondex Mines Acquisition Expiring April 2032 [Member]
Class of Warrant or Right, Outstanding | shares		2,068,000
Subsequent Event [Member] | 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
Subsequent Event [Member] | 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
Subsequent Event [Member] | Maximum [Member]
Leverage Ratio	[1]								4
Subsequent Event [Member] | Maximum [Member] | Letter of Credit [Member]
Letter of Credit, Participation Fee, Percent									3.25%
Subsequent Event [Member] | Minimum [Member] | Letter of Credit [Member]
Letter of Credit, Participation Fee, Percent									2.25%
Klondex Mines Ltd [Member] | Subsequent Event [Member]
Business Acquisition, Share Price | $ / shares		$ 2.24
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		$ 155,200,000
Stock Issued During Period, Shares, New Issues | shares		75,276,176
Business Combination, Subscrition of New Formed Company, Value		$ 8,020,000
Employee Service Share-based Compensation, Cash Flow Effect, Cash Used to Settle Awards		2,000,000
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable		242,400,000
Business Combination, Consideration Transferred, Total		407,700,000
Klondex Mines Ltd [Member] | Subsequent Event [Member] | Hecla Warrants [Member]
Class of Warrant or Right, Issued During Period, Value		10,100,000
Klondex Mines Ltd [Member] | Subsequent Event [Member] | Maximum [Member]
Payments to Acquire Businesses, Gross		$ 153,200,000
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares		75,276,176

[1] The leverage ratio will change to 4.50:1 from September 30, 2018 to December 31, 2019, and will revert back to 4.00:1 effective January 1, 2020.