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Note 6 - Business Segments, Risks and Major Customers (Details Textual)
12 Months Ended
Dec. 31, 2018
$ / Mcf
Dec. 31, 2017
Oil and Gas Delivery Commitments and Contracts, Significant Supplies Dedicated or Contracted to Entity 450,000  
Oil and Gas Delivery Commitments and Contracts, Fixed Price 4.35  
Dominion Field Services, Inc. [Member]    
Productive Gas Wells, Number of Wells, Gross 610  
Interstate Gas Supply, Inc. [Member]    
Productive Gas Wells, Number of Wells, Gross 30  
Product Concentration Risk [Member] | Sales Revenue, Product Line [Member] | Product, Natural Gas [Member]    
Concentration Risk, Percentage 66.00% 73.00%
Product Concentration Risk [Member] | Sales Revenue, Product Line [Member] | Crude Oil and Natural Gas from Operated Wells [Member]    
Concentration Risk, Percentage 71.00% 83.00%
Customer Concentration Risk [Member] | Sales Revenue, Product Line [Member] | Product, Natural Gas [Member]    
Number of Major Customers 2 2
Customer Concentration Risk [Member] | Natural Gas Sales from Operated Wells [Member] | Gas Purchasers [Member]    
Concentration Risk, Percentage 70.00% 76.00%