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Note 6 - Business Segments, Risks and Major Customers (Tables)
12 Months Ended
Dec. 31, 2018
Notes Tables  
Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]
Natural Gas Purchaser
 
2018
   
2017
 
                 
Dominion Field Services, Inc. ("Dominion")
   
43
%
   
44
%
Interstate Gas Supply, Inc. ("IGS")
   
3
     
12
 
     
46
%
   
56
%