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Income Taxes - Additional Information (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Jan. 31, 2018
Jan. 31, 2017
Oct. 31, 2018
Operating Loss Carryforwards [Line Items]      
Income tax expense (benefit) $ (3,035) $ 81  
U.S. federal tax rate 34.00%    
Reduction of valuation allowance attributable to deferred tax assets $ 2,000    
IPR&D      
Operating Loss Carryforwards [Line Items]      
Reduction in deferred tax liability $ 1,000    
Scenario Forecast [Member]      
Operating Loss Carryforwards [Line Items]      
U.S. federal tax rate     21.00%