Summary of Quarterly Operating Results (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended																12 Months Ended
	May 31, 2020	[1]	Feb. 29, 2020	[1]	Nov. 30, 2019	[1]	Aug. 31, 2019	[1]	May 31, 2019	[2]	Feb. 28, 2019	[2]	Nov. 30, 2018	[2]	Aug. 31, 2018	[2]	May 31, 2020		May 31, 2019		May 31, 2018
Selected Quarterly Financial Information [Abstract]
Revenues	$ 17,358		$ 17,487		$ 17,324		$ 17,048		$ 17,807		$ 17,010		$ 17,824		$ 17,052		$ 69,217	[3]	$ 69,693	[3],[4]	$ 65,450	[3],[4]
Operating income	475		411		554		977		1,316		911		1,168		1,071		2,417	[5]	4,466	[6]	4,272	[7]
Net income	$ (334)	[8]	$ 315	[8]	$ 560	[8]	$ 745	[8]	$ (1,969)	[9]	$ 739	[9]	$ 935	[9]	$ 835	[9]	$ 1,286		$ 540		$ 4,572
Basic earnings (loss) per common share	$ (1.28)	[10]	$ 1.21	[10]	$ 2.15	[10]	$ 2.86	[10]	$ (7.56)	[10]	$ 2.83	[10]	$ 3.56	[10]	$ 3.15	[10]	$ 4.92		$ 2.06		$ 17.08
Diluted earnings (loss) per common share	$ (1.28)	[10]	$ 1.20	[10]	$ 2.13	[10]	$ 2.84	[10]	$ (7.56)	[10]	$ 2.80	[10]	$ 3.51	[10]	$ 3.10	[10]	$ 4.90		$ 2.03		$ 16.79

[1] 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.

[2] 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.

[3] 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.

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

[5] Includes TNT Express integration expenses of $270 million. These expenses are included in “Corporate, other and eliminations” and the FedEx Express segment. Also includes noncash goodwill and other asset impairment charges of $435 million primarily related to goodwill impairment at FedEx Office and from the decision to permanently retire certain aircraft and related engines at FedEx Express.

[6] Includes TNT Express integration expenses (including restructuring charges) of $388 million. These expenses are included in “Corporate, other and eliminations” and the FedEx Express segment. Also includes business realignment costs of $320 million included in “Corporate, other and eliminations” and costs incurred in connection with the settlement of a legal matter involving FedEx Ground of $46 million.

[7] Includes TNT Express integration expenses (including restructuring charges) of $477 million. These expenses are included in “Corporate, other and eliminations” and the FedEx Express segment. Also includes goodwill and other asset impairment charges of $380 million included in “Corporate, other and eliminations.”

[8] The fourth quarter of 2020 includes a tax benefit of $71 million in connection with the 2020 U.S. tax loss that can be offset against income in prior years under the CARES Act and a tax expense of $51 million due to a change in deferred tax balances related to foreign tax operations. The second quarter of 2020 includes a tax benefit of $133 million from the reduction of a valuation allowance on certain foreign tax loss carryforwards.

[9] The third quarter of 2019 includes a tax benefit of $90 million from the reduction of a valuation allowance on certain tax loss carryforwards and a tax expense of $50 million related to a lower tax rate in the Netherlands applied to our deferred tax balances. The second quarter of 2019 includes a tax benefit of approximately $60 million from accelerated deductions claimed on our 2018 U.S. income tax return. In addition, we recognized a tax expense of $4 million in the second quarter of 2019 as a revision of the provisional benefit associated with the remeasurement of our net U.S. deferred tax liability upon completion of the accounting for the tax effects of the TCJA.

[10] 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.