Equity method investments - Summarized Financial Information of Equity Method Investments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020
Income Statement [Abstract]
Sales	$ 32,779	$ 31,336	$ 64,217	$ 61,247
Gross profit	6,781	7,017	13,411	13,794
Net earnings (loss)	1,025	952	726	1,793
Share of earnings (loss) from equity method investments	94	40	(1,264)	40
Equity Method Investment
Income Statement [Abstract]
Sales	59,425	53,482	115,527	104,610
Gross profit	2,672	2,182	5,089	4,224
Net earnings (loss)	$ 486	$ 249	$ (4,329)	$ 356