Segment reporting - geographic data (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Aug. 31, 2021	May 31, 2021	Feb. 28, 2021	Nov. 30, 2020	Aug. 31, 2020	May 31, 2020	Feb. 29, 2020	Nov. 30, 2019	Aug. 31, 2021	Aug. 31, 2020	Aug. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales	$ 34,262	$ 34,030	$ 32,779	$ 31,438	$ 30,371	$ 30,364	$ 31,336	$ 29,912	$ 132,509	$ 121,982	$ 120,074
Total long-lived assets	12,247				12,796				12,247	12,796
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales									112,005	107,701	104,532
Total long-lived assets	9,665				10,344				9,665	10,344
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales									8,298	7,830	8,947
Total long-lived assets	2,205				2,203				2,205	2,203
Germany
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales									10,472	4,876	4,713
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Sales									1,734	1,575	$ 1,882
Total long-lived assets	$ 377				$ 250				$ 377	$ 250