Leases - Additional Information (Details) - USD ($) $ in Billions |
12 Months Ended | |
|---|---|---|
May 31, 2020 |
May 31, 2019 |
|
| Lessee Lease Description [Line Items] | ||
| Finance and operating leases expiration term | various dates through 2060 | |
| Percentage total aircraft fleet leased | 5.00% | 6.00% |
| Additional leases not yet commenced, undiscounted future payments | $ 1.6 | |
| Minimum [Member] | ||
| Lessee Lease Description [Line Items] | ||
| Operating lease commencement date | 2021 | |
| Maximum [Member] | ||
| Lessee Lease Description [Line Items] | ||
| Operating lease commencement date | 2022 |