Revenue - Performance Obligations (Details) - USD ($) $ in Millions	Jul. 31, 2020	Apr. 30, 2020
Revenue from Contract with Customer [Abstract]
Expected revenue	$ 4
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-05-01
Revenue from Contract with Customer [Abstract]
Expected revenue	31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected revenue, period		6 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-11-01
Revenue from Contract with Customer [Abstract]
Expected revenue	88
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected revenue, period		1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-11-01
Revenue from Contract with Customer [Abstract]
Expected revenue	68
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected revenue, period		1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-11-01
Revenue from Contract with Customer [Abstract]
Expected revenue	40
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected revenue, period		1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-11-01
Revenue from Contract with Customer [Abstract]
Expected revenue	$ 18
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected revenue, period		1 year