Note 8 - Oil and Gas Leases - Company's Royalty and Working Interests Share (Details)	12 Months Ended
	Dec. 31, 2018 Boe Mcfe	Dec. 31, 2017 Boe Mcfe
Natural Gas, Per Thousand Cubic Feet [Member]
Net oil or gas produced (Thousand Cubic Foot Equivalent) | Mcfe	25,776	42,927
Crude Oil and NGL [Member]
Net oil or gas produced (Thousand Cubic Foot Equivalent) | Boe	6,956	8,169