Commitments - Schedule of Purchase Commitments (Details) $ in Millions	Aug. 31, 2017 USD ($)
Unrecorded Unconditional Purchase Obligation [Line Items]
2018 (remainder)	$ 2,648
2019	2,349
2020	2,417
2021	1,711
2022	1,479
Thereafter	3,383
Total	13,987
Aircraft And Related Equipment Commitments [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
2018 (remainder)	1,398
2019	1,713
2020	1,927
2021	1,335
2022	1,273
Thereafter	2,884
Total	10,530
Other Commitments [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
2018 (remainder)	1,250	[1]
2019	636	[1]
2020	490	[1]
2021	376	[1]
2022	206	[1]
Thereafter	499	[1]
Total	$ 3,457	[1]

[1] Primarily equipment and advertising contracts.