Leases - annual minimum rental commitments (Details) $ in Millions	Aug. 31, 2019 USD ($)
Finance lease obligation
2020	$ 21
2021	21
2022	20
2023	20
2024	20
Later	209
Total minimum lease payments	311
Capital lease
2020	59
2021	60
2022	58
2023	57
2024	58
Later	801
Total minimum lease payments	1,093
Operating lease
2020	3,484
2021	3,323
2022	3,124
2023	2,943
2024	2,771
Later	16,623
Total minimum lease payments	$ 32,268