Retirement Plans - Schedule of Weighted-Average Asset Allocations for U.S Pension Plans and International Pension Plans (Details) - Pension Plans [Member] - USD ($) $ in Millions		May 31, 2020	May 31, 2019	May 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 28,691	$ 24,898
U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 26,978	$ 23,320	$ 22,057
Actual %		100.00%	100.00%
U.S. Plans [Member] | Cash And Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 709	$ 570
Actual %		3.00%	2.00%
U.S. Plans [Member] | Cash And Cash Equivalents [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	[1]	0.00%	0.00%
U.S. Plans [Member] | Cash And Cash Equivalents [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	[1]	5.00%	5.00%
International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 1,713	$ 1,578	1,509
Portion of Fair Value of Plan Assets		$ 1,497	$ 1,374
Actual %		100.00%	100.00%
International Plans [Member] | Cash And Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		$ 9	$ 57
Actual %		1.00%	4.00%
U.S. Large Cap Equity [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 3,070	$ 2,546
Actual %	[2]	11.00%	11.00%
International Equity Securities [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 3,314	$ 3,306
Actual %	[2]	12.00%	14.00%
International Equity Securities [Member] | International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	$ 72	$ 72
Actual %	[2]	5.00%	5.00%
Global Equity Funds [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 1,350	$ 1,451
Actual %	[2]	5.00%	6.00%
Global Equity Funds [Member] | International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	$ 218	$ 206
Actual %	[2]	15.00%	15.00%
U.S. SMID Cap Equity [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 673	$ 731
Actual %		3.00%	3.00%
Corporate Fixed Income Securities [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 7,983	$ 6,794
Actual %		30.00%	29.00%
Corporate Fixed Income Securities [Member] | International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	$ 342	$ 322
Actual %	[2]	23.00%	24.00%
Government Fixed Income Securities [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 6,928	$ 5,384
Actual %	[2]	26.00%	23.00%
Government Fixed Income Securities [Member] | International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	$ 510	$ 438
Actual %	[2]	34.00%	32.00%
Mortgage Backed And Other Fixed Income Securities [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 634	$ 622
Actual %	[2]	2.00%	3.00%
Mortgage Backed And Other Fixed Income Securities [Member] | International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	$ 188	$ 167
Actual %	[2]	12.00%	12.00%
Alternative investments [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 2,264	$ 1,963
Actual %	[2]	8.00%	9.00%
Alternative investments [Member] | U.S. Plans [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	[1],[2]	0.00%	0.00%
Alternative investments [Member] | U.S. Plans [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	[1],[2]	15.00%	15.00%
Other [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 53
Fair Value of Plan Liabilities			$ (47)
Other [Member] | International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	$ 158	$ 112
Actual %	[2]	10.00%	8.00%
Total Equities [Member] | U.S. Plans [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	[1]	30.00%	30.00%
Total Equities [Member] | U.S. Plans [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	[1]	50.00%	50.00%
Total Fixed Income Securities [Member] | U.S. Plans [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	[1]	50.00%	50.00%
Total Fixed Income Securities [Member] | U.S. Plans [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	[1]	70.00%	70.00%
Fair Value, Inputs, Level 1 | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 4,918	$ 4,310
Fair Value, Inputs, Level 1 | U.S. Plans [Member] | Cash And Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		278	50
Fair Value, Inputs, Level 1 | International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		340	357
Fair Value, Inputs, Level 1 | International Plans [Member] | Cash And Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		9	57
Fair Value, Inputs, Level 1 | U.S. Large Cap Equity [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	1,172	875
Fair Value, Inputs, Level 1 | International Equity Securities [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	2,738	2,700
Fair Value, Inputs, Level 1 | U.S. SMID Cap Equity [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		673	730
Fair Value, Inputs, Level 1 | Government Fixed Income Securities [Member] | International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]		290
Fair Value, Inputs, Level 1 | Mortgage Backed And Other Fixed Income Securities [Member] | International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	318
Fair Value, Inputs, Level 1 | Other [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		57
Fair Value of Plan Liabilities			(45)
Fair Value, Inputs, Level 1 | Other [Member] | International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	13	10
Fair Value, Inputs, Level 2 | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		13,233	11,230
Fair Value, Inputs, Level 2 | U.S. Plans [Member] | Cash And Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		431	520
Fair Value, Inputs, Level 2 | International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		63	17
Fair Value, Inputs, Level 2 | U.S. SMID Cap Equity [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets			1
Fair Value, Inputs, Level 2 | Corporate Fixed Income Securities [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		7,983	6,794
Fair Value, Inputs, Level 2 | Government Fixed Income Securities [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	4,652	3,742
Fair Value, Inputs, Level 2 | Mortgage Backed And Other Fixed Income Securities [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	170	175
Fair Value, Inputs, Level 2 | Other [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Liabilities		(3)	(2)
Fair Value, Inputs, Level 2 | Other [Member] | International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	63	17
Fair Value Inputs Level 3 [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		416	302	$ 209
Fair Value Inputs Level 3 [Member] | Alternative investments [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 416	$ 302

[1] ^{Target ranges have not been provided for international plan assets as they are managed at an individual country level.}

[2] ^{Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been classified in the fair value hierarchy but are included in the total.}