Leases - Summary of Components of Net Lease Cost (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
		Feb. 29, 2020	Feb. 29, 2020
Leases [Abstract]
Operating lease cost	[1]	$ 675	$ 2,025
Finance lease cost:
Amortization of right-of-use assets		6	12
Interest on lease liabilities		6	8
Total finance lease cost		12	20
Short-term lease cost		60	141
Variable lease cost	[1]	301	850
Net lease cost		$ 1,048	$ 3,036

[1] Expenses are primarily accounted for in the “Rentals and landing fees” line item. Additional amounts related to embedded leases are accounted for in the “Purchased transportation,” “Fuel” and “Other” line items in the unaudited condensed consolidated statements of income.