Retirement Plans - Schedule of Retirement Plan Costs (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Pension And Other Postretirement Benefit Expense [Abstract]
Defined benefit pension plans, net	$ 38	$ 28	$ 112	$ 85
Defined contribution plans	147	138	425	415
Postretirement healthcare plans	21	19	64	56
Retirement plans costs	$ 206	$ 185	$ 601	$ 556

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