Retirement Plans - Schedule of Retirement Plan Costs (Details) - USD ($) $ in Millions	3 Months Ended
Aug. 31, 2021	Aug. 31, 2020
Pension And Other Postretirement Benefit Expense [Abstract]
Defined benefit pension plans, net	$ (3)	$ 25
Defined contribution plans	180	159
Postretirement healthcare plans	22	21
Retirement plans costs	$ 199	$ 205

The total amount of net periodic benefit cost for defined benefit postretirement healthcare plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain or loss, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments.

No definition available.

Name:	fdx_PostretirementHealthcarePlansNetPeriodicBenefitCost
Namespace Prefix:	fdx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration