Note 9 - Income Taxes - Difference Between Expected Amount and Actual Amount, Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Expected amount	$ (1,865)	$ (17,262)
State income taxes, net of federal benefit	(644)	(3,831)
Percentage depletion	(2,154)	(1,475)
Valuation allowance	1,275	0
Stock-based compensation	67	326
Return to provision adjustments	(60)	(78)
Other	723	(27)
Total income tax benefit	$ (2,658)	$ (22,347)

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

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