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Balance Sheet - Additional Information (Detail)
6 Months Ended 12 Months Ended
Jul. 31, 2017
USD ($)
Customer
Jan. 31, 2017
USD ($)
Customer
Apr. 30, 2017
USD ($)
Installment
Balance Sheet [Line Items]      
Contracts receivable $ 5,823,000 $ 2,752,000  
Number of customers due | Customer 4 3  
Contracts receivable, interest rate 2.90% 2.20%  
Long-term contract receivable for sale of lease pool equipment     $ 3,800,000
Number of installments | Installment     24
Impairment charges related to long-lived assets   $ 0  
Minimum [Member]      
Balance Sheet [Line Items]      
Contracts receivable repayment term 1 month    
Maximum [Member]      
Balance Sheet [Line Items]      
Contracts receivable repayment term 40 months