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Note 3 - Accounts Receivable (Details Textual)
$ in Thousands
3 Months Ended 6 Months Ended 12 Months Ended
Jul. 31, 2021
USD ($)
Apr. 30, 2021
USD ($)
Jul. 31, 2020
Jul. 31, 2021
USD ($)
Jul. 31, 2020
Jan. 31, 2021
USD ($)
Accounts Receivable, Outstanding for Several Years $ 3,700     $ 3,700   $ 3,700
Retention Receivable 3,400     3,400   $ 3,400
Proceeds from Collection of Accounts Receivable Outstanding for Several Years   $ 100        
Allowance for Doubtful Accounts Receivable Outstanding for Several Years $ 0     $ 0    
Revenue Benchmark [Member] | Customer Concentration Risk [Member]            
Number of Major Customers 1   0 0 0  
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | One Customer [Member]            
Concentration Risk, Percentage 12.00%          
Accounts Receivable [Member] | Customer Concentration Risk [Member]            
Number of Major Customers       2   0
Accounts Receivable [Member] | Customer Concentration Risk [Member] | One Customer [Member]            
Concentration Risk, Percentage       22.00%    
Other Noncurrent Assets [Member]            
Retention Receivable $ 2,100     $ 2,100   $ 2,100