Equity method investments - narrative (Details) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	Aug. 18, 2022	May 11, 2022	Aug. 31, 2022	Aug. 31, 2021	Aug. 31, 2020
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investment			$ 559	$ 321	$ 0
Equity earnings (loss)			468	(498)	382
Impairment of equity method investments and investments in debt and equity securities			233	0	0
Share of AOCI of equity method investments
Schedule of Equity Method Investments [Line Items]
Other comprehensive (loss) income before reclassification adjustments			$ (326)	$ (24)	(16)
AmerisourceBergen
Schedule of Equity Method Investments [Line Items]
Percentage of outstanding common shares owned			25.40%	28.50%
Number of shares sold (in shares)		6,000,000
Share price of stock sold (in dollars per share)		$ 150
Proceeds from sale of equity method investments		$ 900
Outstanding shares owned (in shares)			52,854,867	58,854,867
Gain on sale of equity method investment		417
Time period of reporting lag			2 months
Equity earnings (loss)			$ 418	$ (1,100)	341
Equity investment, exceeded its proportionate share of net assets			3,900
AmerisourceBergen | Share of AOCI of equity method investments
Schedule of Equity Method Investments [Line Items]
Other comprehensive (loss) income before reclassification adjustments		$ 32
AmerisourceBergen | Opiod Litigation
Schedule of Equity Method Investments [Line Items]
Equity earnings (loss)				(5,600)
AmerisourceBergen | Level 1
Schedule of Equity Method Investments [Line Items]
Fair value of assets			7,700	7,200
Others
Schedule of Equity Method Investments [Line Items]
Equity earnings (loss)			$ 50	$ 627	$ 31
Option Care Health
Schedule of Equity Method Investments [Line Items]
Percentage of outstanding common shares owned			14.40%	20.50%
Number of shares sold (in shares)	11,000,000
Proceeds from sale of equity method investments	$ 363
Gain on sale of equity method investment	$ 145			$ 290
Equity earnings (loss)				576
Option Care Health | HC Group Holdings I, LLC
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investment				$ 1,200
VillageMD
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investment			$ 2,200
Shields Health Solutions
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investment			402
China
Schedule of Equity Method Investments [Line Items]
Impairment of equity method investments and investments in debt and equity securities			$ 124