Supplemental information - Narrative (Details) - USD ($) shares in Millions, $ in Billions	3 Months Ended		6 Months Ended
	Feb. 28, 2023	Feb. 28, 2022	Feb. 28, 2023	Feb. 28, 2022	Aug. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable from related party	$ 1.4		$ 1.4		$ 1.1
Accumulated depreciation and amortization on property, plant, and equipment	$ 12.8		$ 12.8		12.8
Antidilutive securities excluded from EPS calculations (in shares)	16.0	17.9	16.8	16.9
Incremental common shares attributable to dilutive effect of share-based payment arrangements			4.8
Trade Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivables	$ 4.3		$ 4.3		$ 4.0