Commitments - Schedule of Purchase Commitments (Details) $ in Millions	Aug. 31, 2018 USD ($)
Unrecorded Unconditional Purchase Obligation [Line Items]
2019 (remainder)	$ 2,005
2020	2,777
2021	2,815
2022	2,219
2023	1,824
Thereafter	3,518
Total	15,158
Aircraft And Related Equipment Commitments [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
2019 (remainder)	1,341
2020	1,991
2021	2,315
2022	1,856
2023	1,561
Thereafter	2,986
Total	12,050
Other Commitments [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
2019 (remainder)	664	[1]
2020	786	[1]
2021	500	[1]
2022	363	[1]
2023	263	[1]
Thereafter	532	[1]
Total	$ 3,108	[1]

[1] Primarily equipment and advertising contracts.