Equity method investments - narrative (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
	Dec. 15, 2022	May 31, 2023	Feb. 28, 2022	Aug. 31, 2023	Aug. 31, 2022	Aug. 31, 2021
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investment				$ 1,855	$ 559	$ 321
Equity earnings (loss)				286	468	(498)
Share of OCI of equity method investments
Schedule of Equity Method Investments [Line Items]
Other comprehensive income (loss) before reclassification adjustments				$ 6	$ (326)	(24)
Cencora
Schedule of Equity Method Investments [Line Items]
Investment owned (in shares)				31,800,000	52,900,000
Percentage of outstanding common shares owned				15.90%	25.40%
Proceeds from sale of equity method investments				$ 3,400	$ 900
Gain on sale of equity method investment				1,600	417
Other comprehensive income (loss) before reclassification adjustments				$ (160)	(32)
Time period of reporting lag				2 months
Equity earnings (loss)				$ 252	418	(1,100)
Equity investment, exceeded its proportionate share of net assets				2,400
Cencora | Opiod Litigation
Schedule of Equity Method Investments [Line Items]
Equity earnings (loss)					(5,600)
Cencora | Level 1
Schedule of Equity Method Investments [Line Items]
Fair value of assets				5,600	7,700
Guangzhou Pharmaceuticals
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of equity method investments	$ 150
Option Care Health
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of equity method investments				798	363
Gain on sale of equity method investment		$ 76		$ 186	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
Equity method investment, other than temporary impairment			$ 124
Shields Health Solutions
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investment					$ 402