Basis of Presentation and Other Information Reclassification of prior period amounts (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Reclassification of prior period amounts [Line Items]
Revenue, equipment rentals, net	$ 1,313	$ 1,047	$ 3,778	$ 2,912
Depreciation, equipment rentals	1,137	990	3,454	2,732
Proceeds from Sale and Collection of Receivables			223	909
Payments to Acquire Equipment on Lease			5,739	5,533
Net Cash Provided by (Used in) Financing Activities			(526)	(4,240)
Net Cash Provided by (Used in) Investing Activities			(7,430)	(1,616)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 6,285	4,495	$ 6,285	4,495	$ 6,659	$ 2,942
Accounting Standards Update 2016-15 [Member]
Reclassification of prior period amounts [Line Items]
Net Cash Provided by (Used in) Financing Activities				129
Net Cash Provided by (Used in) Investing Activities				(2)
Adjustments for New Accounting Pronouncement [Member]
Reclassification of prior period amounts [Line Items]
Payments to Acquire Equipment on Lease				3,800
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		55		55		$ 72
Cost of Equipment Rentals [Member]
Reclassification of prior period amounts [Line Items]
Prior Period Reclassification Adjustment		$ 123		$ 347