Note 4 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Jul. 20, 2018
Deferred Tax Liabilities, Net, Total	$ 162,900					$ 162,900
Income Tax Expense (Benefit), Total	(2,679)	$ (5,130)	$ 16,366	$ (28,800)	$ (12,434)	(1,484)	$ (17,564)	$ 20,963	$ 28,090
Net Income (Loss) Attributable to Parent, Total	(23,184)	$ 314	$ (24,948)	25,082	$ 134	(2,870)	$ 447	$ (28,520)	$ 61,569
Klondex Mines Ltd [Member]
Deferred Tax Liabilities, Net, Total										$ 50,100
Income Tax Expense (Benefit), Total	(3,800)					(3,800)
Net Income (Loss) Attributable to Parent, Total	(15,200)					(15,200)
Internal Revenue Service (IRS) [Member] | Domestic Tax Authority [Member]
Deferred Tax Liabilities, Net, Total	46,700					46,700
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount				$ (15,000)
Canada Revenue Agency [Member] | Foreign Tax Authority [Member]
Deferred Tax Liabilities, Net, Total	118,100					118,100
Mexican Tax Authority [Member] | Foreign Tax Authority [Member]
Deferred Tax Assets, Net of Valuation Allowance, Total	$ 1,900					$ 1,900