Note 3 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Income Tax Expense (Benefit), Total	$ 4,634	$ (1,062)
Recognition of Previously Omitted Deferred Income Taxes on Certain State Mining Income Taxes [Member]
Income Tax Expense (Benefit), Total	$ 3,100

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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