Revenue From Contracts With Customers - Narrative (Details) $ in Millions	3 Months Ended	9 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract assets increased due to recognition of revenue related to satisfaction of performance obligations		$ 81
Contract liabilities increased due to revenue recognized in excess of payments received		(5)
Amount of contract liabilities recognized as revenue	$ 2	24
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue expected to be recognized	$ 3,200	$ 3,200
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Period in which revenue is expected to be recognized	1 year	1 year