Summary of Significant Accounting Policies - Revenue Performance Obligations (Details) $ in Millions	Oct. 31, 2019 USD ($)
Summary of Significant Accounting Policies
Remaining performance obligations	$ 24
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-11-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Percentage of remaining performance obligation to be recognized over the next 12 months	70.00%
Period in which remaining performance obligation is expected to be satisfied	12 months