Business Segments and Disaggregated Revenue - Schedule of Geographical Information (Details) - USD ($) $ in Millions		12 Months Ended
		May 31, 2021	May 31, 2020	May 31, 2019	[2]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	[1]	$ 83,959	$ 69,217	$ 69,693
Assets Noncurrent	[1]	62,197	57,154	41,317
U.S. [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	[1]	58,792	48,404	47,584
Assets Noncurrent	[1]	49,407	45,691	33,189
International [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	[1]	25,167	20,813	22,109
Assets Noncurrent	[1]	12,790	11,463	8,128
FedEx Express Segment [Member] | International [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	[1]	23,085	19,177	20,424
FedEx Ground Segment [Member] | International [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	[1]	735	479	467
FedEx Freight Segment [Member] | International [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	[1]	190	192	207
FedEx Services Segment [Member] | International [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	[1]	1	1	1
Other international revenue [Member] | International [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Revenues	[1]	$ 1,156	$ 964	$ 1,010

[1] International revenue includes shipments that either originate in or are destined to locations outside the United States, which could include U.S. payors. Noncurrent assets include property and equipment, goodwill and other long-term assets. Our flight equipment is registered in the U.S. and is included as U.S. assets; however, many of our aircraft operate internationally.

[2] Prior year amounts have been revised to conform to the current year presentation.