Revenues - Practical expedients and other revenue disclosures (Detail) $ in Millions	Mar. 31, 2019 USD ($)
Revenue from remaining performance obligation	$ 297
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01
Revenue from remaining performance obligation	$ 39
Expected period of performance obligation to be recognized	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-07-01
Revenue from remaining performance obligation	$ 133
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	$ 98
Expected period of performance obligation to be recognized	1 year