Leases - future lease payments for operating and finance leases (Details) - USD ($) $ in Millions	Aug. 31, 2021	Aug. 31, 2020
Finance lease
2022	$ 89
2023	88
2024	88
2025	87
2026	86
Later	1,142
Total undiscounted minimum lease payments	1,580
Less: Present value discount	(570)
Lease liability	1,010	$ 1,044
Operating lease
2022	3,439
2023	3,342
2024	3,224
2025	3,102
2026	2,982
Later	15,210
Total undiscounted minimum lease payments	31,299
Less: Present value discount	(6,887)
Lease liability	$ 24,412	$ 24,123