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Note 1 - General and Basis of Presentation 1 (Details Textual) - USD ($)
$ in Thousands
1 Months Ended 3 Months Ended 12 Months Ended
Apr. 30, 2022
Mar. 31, 2022
Mar. 31, 2021
Dec. 31, 2021
Exploration Abandonment and Impairment Expense   $ 0 $ 0  
Cash, FDIC Insured Amount   31,800   $ 31,000
Cash, Uninsured Amount   82,800   64,300
Accounts Receivable, after Allowance for Credit Loss, Current, Total   116,555   $ 122,944
Kenya Power and Lighting Co Limited [Member]        
Accounts Receivable, Past Due   19,800    
Kenya Power and Lighting Co Limited [Member] | Subsequent Event [Member]        
Proceeds, Overdue Accounts Receivable $ 9,400      
ENEE [Member]        
Accounts Receivable, Past Due   $ 20,500    
ENEE [Member] | Subsequent Event [Member]        
Proceeds, Overdue Accounts Receivable $ 4,800      
Accounts Receivable [Member] | Customer Concentration Risk [Member] | Primary Customers [Member]        
Concentration Risk, Percentage   54.00%   58.00%
Non-US [Member]        
Accounts Receivable, after Allowance for Credit Loss, Current, Total   $ 76,800   $ 77,500