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Revenue and Deferred Revenue - Concentration of Net Accounts Receivable Balance (Details) - Accounts Receivable - Customer Concentration Risk
9 Months Ended 12 Months Ended
Oct. 31, 2019
Jan. 31, 2019
Customer A    
Concentration Risk [Line Items]    
Concentration risk, percentage 16.00%  
Customer B    
Concentration Risk [Line Items]    
Concentration risk, percentage   15.00%