Note 13 - Income Taxes - Components of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Loss carryforwards U.S. - Federal/States	$ 22,873	$ 19,512
Asset retirement obligations	3,972	3,523
Accrued expenses	856	725
Equity-based compensation	2,200	2,094
Total deferred tax assets	29,901	25,854
Deferred tax assets, net	29,901	25,854
Deferred tax liabilities:
Depreciation & amortization	(31,663)	(31,119)
Net deferred tax liabilities, net of valuation allowance	$ (1,762)	$ (5,265)