Note 12 - Income Taxes - Components of Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Loss carryforwards U.S. - Federal/States	$ 19,512	$ 17,073
Asset retirement obligations	3,523	3,306
Accrued expenses	725	521
Equity-based compensation	2,094	1,393
Other		4
Total deferred tax assets	25,854	22,297
Deferred tax assets, net	25,854	22,297
Deferred tax liabilities:
Depreciation & amortization	(31,119)	(22,406)
Net deferred tax liabilities, net of valuation allowance	$ (5,265)	$ (109)