Retirement Plans - Schedule of Components of Pension Plans (Details) - Pension Plans [Member] - USD ($) $ in Millions	May 31, 2018	May 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation ("PBO")	$ 24,820	$ 29,913
Fair Value of Plan Assets	23,566	26,312
Funded Status	(1,254)	(3,601)
Qualified [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation ("PBO")	22,413	27,600
Fair Value of Plan Assets	22,057	24,933
Funded Status	(356)	(2,667)
Nonqualified [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation ("PBO")	240	270
Funded Status	(240)	(270)
International Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected Benefit Obligation ("PBO")	2,167	2,043
Fair Value of Plan Assets	1,509	1,379
Funded Status	$ (658)	$ (664)

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

Name:	us-gaap_DefinedBenefitPlanBenefitObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ References

+ Details

Name:	us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64852052&loc=d3e1703-114919

+ Details

Name:	us-gaap_DefinedBenefitPlanFundedStatusOfPlan
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	fdx_PensionPlansComponentsAxis=fdx_QualifiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	fdx_PensionPlansComponentsAxis=fdx_NonqualifiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	fdx_PensionPlansComponentsAxis=fdx_InternationalPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: