Commitments - Additional Information (Details) $ in Millions	3 Months Ended	6 Months Ended
	Nov. 30, 2017 USD ($) air-craft	Nov. 30, 2017 USD ($) air-craft
Other Aircraft Commitments Disclosure [Abstract]
Boeing 767F Conditional Aircraft Commitments		4
Boeing 777F Conditional Aircraft Commitments		6
Deposit and Progress Payments | $	$ 684	$ 684
Cessna SkyCourier 408 [Member]
Other Aircraft Commitments Disclosure [Abstract]
Number of aircraft agreed to purchase	50	50
Additional maximum number of aircraft, options to purchase	50	50
Aircraft expected to be delivered, earliest fiscal year	2021
Aircraft expected to be delivered, latest fiscal year	2024
ATR 72-600F [Member]
Other Aircraft Commitments Disclosure [Abstract]
Number of aircraft agreed to purchase	30	30
Additional maximum number of aircraft, options to purchase	20	20
Aircraft expected to be delivered, earliest fiscal year	2021
Aircraft expected to be delivered, latest fiscal year	2026