Equity method investments - Narrative (Details) - USD ($) shares in Millions, $ in Millions									3 Months Ended			9 Months Ended
	Jun. 15, 2023	Jun. 08, 2023	May 11, 2023	Mar. 03, 2023	Dec. 15, 2022	Dec. 13, 2022	Nov. 10, 2022	May 11, 2022	May 31, 2023	Feb. 28, 2022	Nov. 30, 2021	May 31, 2023	May 31, 2022	Aug. 31, 2022
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investments												$ 1,691	$ 421
Pledged collateral (in shares)			4.6
Impairment of equity method investments and investments in debt and equity securities												$ 16	$ 233
Subsequent Event
Schedule of Equity Method Investments [Line Items]
Pledged collateral (in shares)	2.2
Shields Health Solutions Parent, LLC
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investments											$ 402
VillageMD
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investments										$ 2,200
Impairment of equity method investments and investments in debt and equity securities									$ 124
AmerisourceBergen
Schedule of Equity Method Investments [Line Items]
Ownership percentage									16.50%			16.50%		25.40%
Number of shares sold (in shares)			0.3			6.0	13.2	6.0
Proceeds from sale of equity method investments			$ 50			$ 984	$ 2,000	$ 900
Gain on sale of equity method investments			25			492	969	424
Other comprehensive (loss) income before reclassification adjustments			$ 2			$ 40	$ 110	$ (25)
Period of reporting lag												2 months
Equity investment, exceeded its proportionate share of net assets									$ 2,600			$ 2,600
AmerisourceBergen | Investment, Affiliated Issuer
Schedule of Equity Method Investments [Line Items]
Investment owned, shares (in shares)									33.4			33.4		52.9
AmerisourceBergen | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Number of shares sold (in shares)	0.3
Proceeds from sale of equity method investments	$ 50
AmerisourceBergen | Level 1
Schedule of Equity Method Investments [Line Items]
Fair market value of equity investment									$ 5,700			$ 5,700		$ 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]
Number of shares sold (in shares)				15.5
Proceeds from sale of equity method investments				$ 469
Percentage of outstanding common stock				6.00%										14.40%
Gain on sale of equity method investments				$ 154					$ 76
Option Care Health | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Number of shares sold (in shares)		10.8
Proceeds from sale of equity method investments		$ 330