Retirement Plans - Schedule of Weighted-Average Asset Allocations for U.S Pension Plans and International Pension Plans (Details) - USD ($) $ in Millions		12 Months Ended
		May 31, 2017		May 31, 2016		May 31, 2015
U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 24,933		$ 23,017		$ 23,006
Actual %		100.00%		100.00%
International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 1,379		$ 1,254		$ 499
Portion of Fair Value of Plan Assets		$ 1,206		$ 1,092
Actual %		100.00%		100.00%
Fair Value Inputs Level 1 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 4,429		$ 4,119
Fair Value Inputs Level 1 [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		95		203
Fair Value Inputs Level 2 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		12,955		12,499
Fair Value Inputs Level 2 [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		398		396
Fair Value Inputs Level 3 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		129		48
Cash And Cash Equivalents [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 1,076		$ 568
Actual %		4.00%		2.00%
Target %	[1]	0 - 5%		0 - 5%
Cash And Cash Equivalents [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		$ 48		$ 211
Actual %		4.00%		19.00%
Cash And Cash Equivalents [Member] | Fair Value Inputs Level 1 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 26		$ 76
Cash And Cash Equivalents [Member] | Fair Value Inputs Level 1 [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		2		157
Cash And Cash Equivalents [Member] | Fair Value Inputs Level 2 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		1,050		492
Cash And Cash Equivalents [Member] | Fair Value Inputs Level 2 [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		46		54
U.S. Large Cap Equity [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 2,415		$ 3,257
Actual %	[2]	10.00%		14.00%
U.S. Large Cap Equity [Member] | Fair Value Inputs Level 1 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 830		$ 750
International Equity Securities [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 3,521		$ 3,381
Actual %	[2]	14.00%		15.00%
International Equity Securities [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	$ 137		$ 124
Actual %	[2]	11.00%		11.00%
International Equity Securities [Member] | Fair Value Inputs Level 1 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 2,747		$ 2,685
International Equity Securities [Member] | Fair Value Inputs Level 2 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	157		121
International Equity Securities [Member] | Fair Value Inputs Level 2 [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	72		63
Global Equity Funds [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 3,276		$ 2,794
Actual %	[2]	13.00%		12.00%
Global Equity Funds [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	$ 202		$ 148
Actual %	[2]	17.00%		14.00%
U.S. SMID Cap Equity [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 987		$ 913
Actual %		4.00%		4.00%
U.S. SMID Cap Equity [Member] | Fair Value Inputs Level 1 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 987		$ 913
Corporate Fixed Income Securities [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 8,163		$ 6,608
Actual %		33.00%		29.00%
Corporate Fixed Income Securities [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	$ 270		$ 122
Actual %	[2]	22.00%		11.00%
Corporate Fixed Income Securities [Member] | Fair Value Inputs Level 2 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 8,163		$ 6,608
Corporate Fixed Income Securities [Member] | Fair Value Inputs Level 2 [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	49		44
Government Fixed Income Securities [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ 4,674	[2]	$ 5,148
Actual %		19.00%	[2]	22.00%
Government Fixed Income Securities [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	$ 405		$ 324
Actual %	[2]	34.00%		30.00%
Government Fixed Income Securities [Member] | Fair Value Inputs Level 1 [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	$ 95		$ 60
Government Fixed Income Securities [Member] | Fair Value Inputs Level 2 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		3,454	[2]	5,148
Government Fixed Income Securities [Member] | Fair Value Inputs Level 2 [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	230		213
Mortgage Backed And Other Fixed Income Securities [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 603		$ 347
Actual %	[2]	2.00%		2.00%
Mortgage Backed And Other Fixed Income Securities [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets	[2]	$ 145		$ 134
Actual %	[2]	12.00%		12.00%
Mortgage Backed And Other Fixed Income Securities [Member] | Fair Value Inputs Level 2 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 129		$ 146
Alternative investments [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	$ 377		$ 322
Actual %	[2]	2.00%		1.00%
Target %	[1],[2]	0 - 5		0 - 5
Alternative investments [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		$ 17		$ 39	[2]
Actual %		1.00%		4.00%	[2]
Alternative investments [Member] | Fair Value Inputs Level 2 [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		$ 17		$ 18	[2]
Alternative investments [Member] | Fair Value Inputs Level 3 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets	[2]	129		48
Other [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ (159)		$ (321)
Actual %		(1.00%)		(1.00%)
Other [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		$ (18)		$ (10)
Actual %		(1.00%)		(1.00%)
Other [Member] | Fair Value Inputs Level 1 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		$ (161)		$ (305)
Other [Member] | Fair Value Inputs Level 1 [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		(2)		(14)
Other [Member] | Fair Value Inputs Level 2 [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair Value of Plan Assets		2		(16)
Other [Member] | Fair Value Inputs Level 2 [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Portion of Fair Value of Plan Assets		$ (16)		$ 4
Total Equities [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	[1]	30 - 50		35 - 55
Total Fixed Income Securities [Member] | U.S. Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Target %	[1]	50 - 70		45 - 65

[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.