Note 6 - Income Taxes (Details Textual) - USD ($) $ in Thousands	11 Months Ended	12 Months Ended
	Dec. 13, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Liabilities, Net, Total		$ 129,563	$ 134,745
Income Tax Expense (Benefit), Total		135	(24,101)	$ (6,701)
Deferred Tax Assets, Valuation Allowance, Total		$ 77,210	86,634	$ 94,981	$ 78,684
Operating Loss Carryforwards Expiration Period (Year)		20 years
Unrecognized Tax Benefits, Ending Balance		$ 0	0
Domestic Tax Authority [Member]
Deferred Tax Assets, Valuation Allowance, Total		72,500
Operating Loss Carryforwards, Total		788,200
Operating Loss Carryforwards, Indefinite Carryforward Period		292,900
Foreign Tax Authority [Member]
Operating Loss Carryforwards, Total		53,500
Foreign Tax Authority [Member] | Canada Revenue Agency [Member]
Deferred Tax Assets, Valuation Allowance, Total		2,600
Foreign Tax Authority [Member] | Mexican Tax Authority [Member]
Deferred Tax Assets, Valuation Allowance, Total		2,100
State and Local Jurisdiction [Member]
Operating Loss Carryforwards, Total		477,900
Klondex Mines Ltd [Member]
Deferred Tax Liabilities, Net, Total		59,500
Income Tax Expense (Benefit), Total	$ (6,300)	$ (4,400)	$ (15,200)