Commitments - Additional Information (Details) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 29, 2020 USD ($) air-craft	Aug. 31, 2019 air-craft	Feb. 29, 2020 USD ($) air-craft
Other Aircraft Commitments Disclosure [Abstract]
Deposit and Progress Payments | $	$ 733		$ 733
B767F [Member]
Other Aircraft Commitments Disclosure [Abstract]
Conditional Aircraft Commitments			3
Number of additional aircraft agreed to purchase options exercised		6
Aircraft expected to be delivered, fiscal year		2022
B777F [Member]
Other Aircraft Commitments Disclosure [Abstract]
Conditional Aircraft Commitments			6
B777F Aircraft from 2023 to 2022 [Member]
Other Aircraft Commitments Disclosure [Abstract]
Number of aircrafts rescheduled delivery	2		2
Aircraft expected to be delivered, earliest fiscal year	2022
Aircraft expected to be delivered, latest fiscal year	2023
B767F Aircraft from 2022 to 2023 [Member]
Other Aircraft Commitments Disclosure [Abstract]
Number of aircrafts rescheduled delivery	2		2
Aircraft expected to be delivered, earliest fiscal year	2022
Aircraft expected to be delivered, latest fiscal year	2023