Note 8 - Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss	$ 32,659	$ 24,081
Valuation allowance	(4,651)	(1,275)
Capital loss carryforward	0	525
Stock-based compensation	0	179
Other	0	234
Total deferred tax assets	28,008	23,744
Coal properties	(30,368)	(26,171)
Investment in partnerships	(484)	(397)
Other	(6)	0
Total deferred tax liabilities	(30,858)	(26,568)
Net deferred tax liability	$ (2,850)	$ (2,824)