Computation of Earnings Per Share - Schedule of Basic and Diluted Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended																12 Months Ended
		May 31, 2020	[2],[3]	Feb. 29, 2020	[2],[3]	Nov. 30, 2019	[2],[3]	Aug. 31, 2019	[2],[3]	May 31, 2019	[3],[4]	Feb. 28, 2019	[3],[4]	Nov. 30, 2018	[3],[4]	Aug. 31, 2018	[3],[4]	May 31, 2020	May 31, 2019	May 31, 2018
Basic earnings per common share:
Net earnings allocable to common shares	[1]																	$ 1,284	$ 539	$ 4,566
Weighted-average common shares																		261.0	262.0	267.0
Basic earnings (loss) per common share		$ (1.28)		$ 1.21		$ 2.15		$ 2.86		$ (7.56)		$ 2.83		$ 3.56		$ 3.15		$ 4.92	$ 2.06	$ 17.08
Diluted earnings per common share:
Net earnings allocable to common shares	[1]																	$ 1,284	$ 539	$ 4,566
Weighted-average common shares																		261.0	262.0	267.0
Dilutive effect of share-based awards																		1.0	3.0	5.0
Weighted-average diluted shares																		262.0	265.0	272.0
Diluted earnings (loss) per common share		$ (1.28)		$ 1.20		$ 2.13		$ 2.84		$ (7.56)		$ 2.80		$ 3.51		$ 3.10		$ 4.90	$ 2.03	$ 16.79
Anti-dilutive options excluded from diluted earnings per common share																		11.7	5.4	2.5

[1] Net earnings available to participating securities were immaterial in all periods presented.

[2] The fourth quarter, third quarter, second quarter and first quarter of 2020 include $63 million, $72 million, $64 million and $71 million, respectively, of TNT Express integration expenses. The fourth quarter includes $369 million of goodwill and other asset impairment charges associated with the FedEx Office and FedEx Logistics operating segments and a net loss of $794 million related to the annual MTM retirement plans accounting adjustment. The second quarter of 2020 includes asset impairment charges of $66 million related to the permanent retirement of 10 Airbus A310-300 aircraft and 12 related engines at FedEx Express.

[3] The sum of the quarterly earnings per share may not equal annual amounts due to differences in the weighted-average number of shares outstanding during the respective periods.

[4] The fourth quarter, third quarter, second quarter and first quarter of 2019 include $84 million, $69 million, $114 million and $121 million, respectively, of TNT Express integration expenses (including any restructuring charges). The fourth quarter and third quarter of 2019 include business realignment costs of $316 million and $4 million, respectively. The fourth quarter includes a net loss of $3.9 billion related to the annual MTM retirement plans accounting adjustment. The second quarter of 2019 includes costs incurred in connection with the settlement of a legal matter involving FedEx Ground of $46 million.