Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
Feb. 29, 2020	Feb. 28, 2019
Condensed Cash Flow Statements Captions [Line Items]
CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES	$ 3,278	$ 3,323
INVESTING ACTIVITIES
Capital expenditures	(4,705)	(3,757)
Proceeds from asset dispositions and other	15	62
Cash used in investing activities	(4,690)	(3,695)
FINANCING ACTIVITIES
Proceeds from short-term borrowings, net	298	220
Principal payments on debt	(1,045)	(874)
Proceeds from debt issuances	2,093	2,463
Proceeds from stock issuances	38	58
Dividends paid	(509)	(514)
Purchase of treasury stock	(3)	(1,365)
Other, net	(5)	5
Cash provided by (used in) financing activities	867	(7)
Effect of exchange rate changes on cash	(8)	(14)
Net decrease in cash and cash equivalents	(553)	(393)
Cash and cash equivalents at beginning of period	2,319	3,265
Cash and cash equivalents at end of period	1,766	2,872
Consolidation Eliminations [Member]
Condensed Cash Flow Statements Captions [Line Items]
CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES	30	(26)
FINANCING ACTIVITIES
Net decrease in cash and cash equivalents	30	(26)
Cash and cash equivalents at beginning of period	(46)	(15)
Cash and cash equivalents at end of period	(16)	(41)
Parent Company [Member] \| Reportable Legal Entities [Member]
Condensed Cash Flow Statements Captions [Line Items]
CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES	(1,794)	(109)
INVESTING ACTIVITIES
Capital expenditures	(2)	(3)
Proceeds from asset dispositions and other	(12)	(45)
Cash used in investing activities	(14)	(48)
FINANCING ACTIVITIES
Proceeds from short-term borrowings, net	298	220
Net transfers from (to) Parent	597	2
Payment on loan between subsidiaries	(326)	(29)
Principal payments on debt	(956)	(750)
Proceeds from debt issuances	2,093	2,463
Proceeds from stock issuances	38	58
Dividends paid	(509)	(514)
Purchase of treasury stock	(3)	(1,365)
Other, net	(4)
Cash provided by (used in) financing activities	1,228	85
Net decrease in cash and cash equivalents	(580)	(72)
Cash and cash equivalents at beginning of period	826	1,485
Cash and cash equivalents at end of period	246	1,413
Guarantor Subsidiaries [Member] \| Reportable Legal Entities [Member]
Condensed Cash Flow Statements Captions [Line Items]
CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES	4,864	3,136
INVESTING ACTIVITIES
Capital expenditures	(4,288)	(3,359)
Proceeds from asset dispositions and other	20	86
Cash used in investing activities	(4,268)	(3,273)
FINANCING ACTIVITIES
Net transfers from (to) Parent	(869)	(31)
Intercompany dividends	398	114
Principal payments on debt	(81)	(117)
Other, net		127
Cash provided by (used in) financing activities	(552)	93
Effect of exchange rate changes on cash	1	(9)
Net decrease in cash and cash equivalents	45	(53)
Cash and cash equivalents at beginning of period	158	257
Cash and cash equivalents at end of period	203	204
Non-guarantor Subsidiaries [Member] \| Reportable Legal Entities [Member]
Condensed Cash Flow Statements Captions [Line Items]
CASH PROVIDED BY (USED IN) OPERATING ACTIVITIES	178	322
INVESTING ACTIVITIES
Capital expenditures	(415)	(395)
Proceeds from asset dispositions and other	7	21
Cash used in investing activities	(408)	(374)
FINANCING ACTIVITIES
Net transfers from (to) Parent	272	29
Payment on loan between subsidiaries	326	29
Intercompany dividends	(398)	(114)
Principal payments on debt	(8)	(7)
Other, net	(1)	(122)
Cash provided by (used in) financing activities	191	(185)
Effect of exchange rate changes on cash	(9)	(5)
Net decrease in cash and cash equivalents	(48)	(242)
Cash and cash equivalents at beginning of period	1,381	1,538
Cash and cash equivalents at end of period	$ 1,333	$ 1,296

The net cash inflow (outflow) from parent as a source of financing.

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

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The distributions of earnings to an entity that is affiliated with the reporting entity by means of direct or indirect ownership.

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The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

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