Basis of Presentation and Other Information Reclassification of prior period amounts (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2019	Mar. 31, 2018
Reclassification of prior period amounts [Line Items]
Revenue, equipment rentals, net	$ 1,330	$ 1,253	$ 2,689	$ 2,465
Depreciation, equipment rentals	1,056	1,181	2,085	2,317
Proceeds from Sale and Collection of Receivables			0	223
Payments to Acquire Equipment on Lease			3,302	3,524
Net Cash Provided by (Used in) Financing Activities			(2,507)	44
Net Cash Provided by (Used in) Investing Activities			(5,020)	(6,287)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 4,346	$ 5,773	$ 4,346	$ 5,773	$ 7,063	$ 6,659