Revenues - Practical expedients and other revenue disclosures (Detail) $ in Millions	Sep. 30, 2019 USD ($)
Revenue from remaining performance obligation	$ 510
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-07-01
Revenue from remaining performance obligation	$ 164
Expected period of performance obligation to be recognized	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-07-01
Revenue from remaining performance obligation	$ 152
Expected period of performance obligation to be recognized	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-07-01
Revenue from remaining performance obligation	$ 56
Expected period of performance obligation to be recognized	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-07-01
Revenue from remaining performance obligation	$ 24
Expected period of performance obligation to be recognized	1 year