Receivables - Sale of Receivables (Details) - USD ($)	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 21, 2016
Receivables [Abstract]
Accounts receivable securitization facility, amount			$ 600,000,000
Availability under securitization facility	$ 434,000,000
Drawn amount	413,000,000
Receivable	$ 21,000,000
Length of extension	1 year
Gain (loss) on sale of receivables	$ 0	$ 0
Transfer of Financial Assets Accounted for as Sales, Deferred Purchase Price [Roll Forward]
Deferred purchase price receivable, Beginning balance	233,000,000	252,000,000
Transfers of receivables	5,435,000,000	2,192,000,000
Collections	(4,393,000,000)	(2,225,000,000)
Change in funding availability	(246,000,000)	30,000,000
Facility amendments	(457,000,000)	0
Fair value adjustment	2,000,000	(16,000,000)
Deferred purchase price receivable, Ending balance	574,000,000	$ 233,000,000
Transfers of receivables	464,000,000
Collections	521,000,000
Operating cash flow effect	$ (57,000,000)