Retirement Plans - Reconciliation of Changes In Pension And Postretirement Healthcare Plans Benefit Obligations And Fair Value Of Assets (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]
Accumulated Benefit Obligation (“ABO”)	$ 27,244	$ 27,236
Changes in Projected Benefit Obligation (“PBO”) and Accumulated Postretirement Benefit Obligation (“APBO”)
PBO/APBO at the beginning of year	27,804	26,636
Service cost	638	622	$ 615
Interest cost	1,128	1,155	1,068
Actuarial loss	571	284
Benefits paid	(2,271)	(893)
PBO/APBO at the end of year	27,870	27,804	26,636
Change in Plan Assets
Balance at beginning of year	23,017	23,006
Actual return on plan assets	2,167	211
Company contributions	2,020	693
Benefits paid	(2,271)	(893)
Balance at end of year	24,933	23,017	23,006
Funded Status of the Plans	(2,937)	(4,787)
Amount Recognized in the Balance Sheet at May 31:
Current pension, postretirement healthcare and other benefit obligations	(33)	(19)
Noncurrent pension, postretirement healthcare and other benefit obligations	(2,904)	(4,768)
Net amount recognized	(2,937)	(4,787)
Amounts Recognized in AOCI and not yet reflected in Net Periodic Benefit Cost:
Prior service credit and other	(410)	(528)
Defined Benefit Plan Amounts That Will Be Amortized From Accumulated Other Comprehensive Income Loss In Next Fiscal Year Abstract
Prior service credit and other	(118)	(118)
International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation (“ABO”)	1,842	1,609
Changes in Projected Benefit Obligation (“PBO”) and Accumulated Postretirement Benefit Obligation (“APBO”)
PBO/APBO at the beginning of year	1,798	876
Service cost	83	40	38
Interest cost	43	25	28
Actuarial loss	161	(7)
Benefits paid	(38)	(19)
Business acquisition		907
Purchase accounting adjustment	26
Other	(30)	(24)
PBO/APBO at the end of year	2,043	1,798	876
Change in Plan Assets
Balance at beginning of year	1,254	499
Actual return on plan assets	112	12
Company contributions	95	33
Benefits paid	(38)	(19)
Business acquisition		761
Other	(44)	(32)
Balance at end of year	1,379	1,254	499
Funded Status of the Plans	(664)	(544)
Amount Recognized in the Balance Sheet at May 31:
Noncurrent asset	40	53
Current pension, postretirement healthcare and other benefit obligations	(17)	(12)
Noncurrent pension, postretirement healthcare and other benefit obligations	(687)	(585)
Net amount recognized	(664)	(544)
Amounts Recognized in AOCI and not yet reflected in Net Periodic Benefit Cost:
Prior service credit and other	(13)	(18)
Defined Benefit Plan Amounts That Will Be Amortized From Accumulated Other Comprehensive Income Loss In Next Fiscal Year Abstract
Prior service credit and other	(2)	(3)
Postretirement Healthcare Plans [Member]
Changes in Projected Benefit Obligation (“PBO”) and Accumulated Postretirement Benefit Obligation (“APBO”)
PBO/APBO at the beginning of year	905	929
Service cost	36	40	40
Interest cost	39	42	41
Actuarial loss	(14)	(64)
Benefits paid	(72)	(78)
Other	33	36
PBO/APBO at the end of year	927	905	$ 929
Change in Plan Assets
Company contributions	36	42
Benefits paid	(72)	(78)
Other	36	36
Funded Status of the Plans	(927)	(905)
Amount Recognized in the Balance Sheet at May 31:
Current pension, postretirement healthcare and other benefit obligations	(39)	(40)
Noncurrent pension, postretirement healthcare and other benefit obligations	(888)	(865)
Net amount recognized	(927)	$ (905)
Amounts Recognized in AOCI and not yet reflected in Net Periodic Benefit Cost:
Prior service credit and other	$ (4)