Income Taxes - Summary of Reconciliation of Effective Tax Rates (Details)		3 Months Ended		9 Months Ended
		Feb. 28, 2019	Feb. 28, 2018	Feb. 28, 2019	Feb. 28, 2018
Operating Loss Carryforwards [Line Items]
Effective tax rate	[1]	20.60%	(137.30%)	21.80%	(15.00%)
Remeasurement of net U.S. deferred tax liability in 2018		131.50%		38.50%
Effect of February 2018 pension contribution	[2]	23.30%		6.80%
Reduction of valuation allowance on tax loss carryforwards in 2019		(10.30%)		(3.00%)
Remeasurement of net Dutch deferred tax asset in 2019		5.30%		1.50%
Transition tax provisional benefit in 2018		4.10%		1.20%
Foreign tax credits on foreign dividends in 2018		1.20%		2.90%
Accelerated deductions claimed in 2019 on the 2018 U.S. income tax return				(1.80%)
Other, net	[3]	(2.10%)		(1.70%)
2018 [Member]
Operating Loss Carryforwards [Line Items]
Lower statutory tax rate	[4]	12.50%
2019 [Member]
Operating Loss Carryforwards [Line Items]
Lower statutory tax rate	[4]	(7.60%)		(7.60%)

[1] 2018 includes a blended U.S. statutory federal income tax rate of 29.2% while 2019 includes the fully phased-in rate of 21%.

[2] The benefit is from the pension contribution deducted on our 2017 tax return at a tax rate of 35%.

[3] The 2018 tax rates were negatively impacted by the effect of the NotPetya cyberattack, costs incurred in connection with the integration of foreign operations of FedEx Express and TNT Express B.V. (“TNT Express”), changes in uncertain tax positions and tax rate impacts on changes in deferred tax items after the TCJA enactment, and were favorably impacted from tax benefits from share-based payments

[4] Due to our May 31 fiscal year-end, the TCJA’s lower U.S. statutory federal income tax rate that went into effect on December 22, 2017 was phased in resulting in a rate of 29.2% for 2018 and a rate of 21% for subsequent years