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Description of Business and Basis of Presentation - Additional Information (Details)
$ in Thousands
3 Months Ended 6 Months Ended 12 Months Ended
Jul. 31, 2017
USD ($)
Customer
Jul. 31, 2016
Customer
Jul. 31, 2017
USD ($)
Customer
Jul. 31, 2016
Customer
Jan. 31, 2017
USD ($)
Customer
Organization Consolidation And Presentation Of Financial Statements [Line Items]          
Restricted cash | $ $ 26,543   $ 26,543   $ 26,781
Excess tax benefits from employee stock option exercises included in net operating loss and research and development tax credit forwards | $     $ 25,200    
Credit Concentration Risk | Accounts Receivable          
Organization Consolidation And Presentation Of Financial Statements [Line Items]          
Number of major customer | Customer 1   1   2
Concentration risk percentage     10.00%   10.00%
Customer Concentration Risk | Revenue          
Organization Consolidation And Presentation Of Financial Statements [Line Items]          
Number of major customer | Customer 0 0 0 0  
Concentration risk percentage 10.00% 10.00% 10.00% 10.00%  
Geographic Concentration Risk | Revenue | Non-U.S.          
Organization Consolidation And Presentation Of Financial Statements [Line Items]          
Concentration risk percentage 21.00% 17.00% 21.00% 17.00%  
Geographic Concentration Risk | Revenue | United States          
Organization Consolidation And Presentation Of Financial Statements [Line Items]          
Concentration risk percentage 79.00% 83.00% 79.00% 83.00%  
Geographic Concentration Risk | Property and Equipment | United States          
Organization Consolidation And Presentation Of Financial Statements [Line Items]          
Concentration risk percentage     99.70%   99.70%