Retirement Plans - Reconciliation of Changes In Pension And Postretirement Healthcare Plans Benefit Obligations And Fair Value Of Assets (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Feb. 28, 2018	May 31, 2019	May 31, 2018	May 31, 2017
U.S. Plans [Member]
Change in Plan Assets
Company contributions	$ 1,500	$ 1,000	$ 2,500
Pension Plans [Member]
Changes in Projected Benefit Obligation (“PBO”) and Accumulated Postretirement Benefit Obligation (“APBO”)
PBO/APBO at the beginning of year		24,820
PBO/APBO at the end of year		28,855	24,820
Change in Plan Assets
Balance at beginning of year		23,566
Balance at end of year		24,898	23,566
Funded Status of the Plans		(3,957)	(1,254)
Pension Plans [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation (“ABO”)		25,915	22,029
Changes in Projected Benefit Obligation (“PBO”) and Accumulated Postretirement Benefit Obligation (“APBO”)
PBO/APBO at the beginning of year		22,653	27,870
Service cost		689	679	$ 638
Interest cost		951	1,115	1,128
Actuarial loss		3,016	21
Benefits paid		(755)	(854)
Settlements			(6,178)
PBO/APBO at the end of year		26,554	22,653	27,870
Change in Plan Assets
Balance at beginning of year		22,057	24,933
Actual return on plan assets		984	1,609
Company contributions		1,034	2,547
Benefits paid		(755)	(854)
Settlements			(6,178)
Balance at end of year		23,320	22,057	24,933
Funded Status of the Plans		(3,234)	(596)
Amount Recognized in the Balance Sheet at May 31:
Current pension, postretirement healthcare and other benefit obligations		(70)	(22)
Noncurrent pension, postretirement healthcare and other benefit obligations		(3,164)	(574)
Net amount recognized		(3,234)	(596)
Amounts Recognized in AOCI and not yet reflected in Net Periodic Benefit Cost:
Prior service (credit) cost and other		(173)	(292)
Pension Plans [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation (“ABO”)		2,084	1,956
Changes in Projected Benefit Obligation (“PBO”) and Accumulated Postretirement Benefit Obligation (“APBO”)
PBO/APBO at the beginning of year		2,167	2,043
Service cost		94	97	83
Interest cost		49	49	43
Actuarial loss		127	(34)
Benefits paid		(38)	(46)
Settlements		(13)	(5)
Other		(85)	63
PBO/APBO at the end of year		2,301	2,167	2,043
Change in Plan Assets
Balance at beginning of year		1,509	1,379
Actual return on plan assets		94	49
Company contributions		91	84
Benefits paid		(38)	(46)
Settlements		(13)	(5)
Other		(65)	48
Balance at end of year		1,578	1,509	1,379
Funded Status of the Plans		(723)	(658)
Amount Recognized in the Balance Sheet at May 31:
Noncurrent asset		82	73
Current pension, postretirement healthcare and other benefit obligations		(16)	(16)
Noncurrent pension, postretirement healthcare and other benefit obligations		(789)	(715)
Net amount recognized		(723)	(658)
Amounts Recognized in AOCI and not yet reflected in Net Periodic Benefit Cost:
Prior service (credit) cost and other		(6)	(10)
Postretirement Healthcare Plans [Member]
Changes in Projected Benefit Obligation (“PBO”) and Accumulated Postretirement Benefit Obligation (“APBO”)
PBO/APBO at the beginning of year		955	927
Service cost		35	36	36
Interest cost		40	39	39
Actuarial loss		266	(9)
Benefits paid		(123)	(80)
Other		48	42
PBO/APBO at the end of year		1,221	955	$ 927
Change in Plan Assets
Company contributions		73	42
Benefits paid		(123)	(80)
Other		50	38
Funded Status of the Plans		(1,221)	(955)
Amount Recognized in the Balance Sheet at May 31:
Current pension, postretirement healthcare and other benefit obligations		(87)	(62)
Noncurrent pension, postretirement healthcare and other benefit obligations		(1,134)	(893)
Net amount recognized		(1,221)	(955)
Amounts Recognized in AOCI and not yet reflected in Net Periodic Benefit Cost:
Prior service (credit) cost and other		$ 1	$ 2