Note 13 - Income Taxes - Reconciliation of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes computed at the federal statutory rate	$ 9,325	$ (1,762)	$ 6,320
State taxes, net of federal benefits	796	(253)	945
State tax rate changes, net of federal benefits	(2,274)
Percentage depletion	(3,363)	(714)	(2,093)
Changes in tax status		(1,773)
Change in enacted tax rates	(194)	473	109
Other, net	357	545	(118)
Total income tax expense (benefit)	$ 4,647	$ (3,484)	$ 5,163