Equity method and other investments - Narrative (Details) - USD ($) shares in Millions, $ in Millions		1 Months Ended	3 Months Ended			6 Months Ended	9 Months Ended		12 Months Ended
	Jun. 09, 2025	Jun. 25, 2025	May 31, 2025	Feb. 28, 2025	May 31, 2024	Nov. 09, 2023	May 31, 2025	May 31, 2024	Aug. 31, 2024
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investments							$ 391	$ 847
Walgreens Boots Alliance, Inc. | Cencora
Schedule of Equity Method Investments [Line Items]
Stock repurchased during period, value				$ 50
Derivatives not designated as hedges:
Schedule of Equity Method Investments [Line Items]
Pledged collateral (in shares)						10.4
Cencora
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of equity method investments				315	$ 400			1,600
Gain on sale of equity method investments				$ 204	$ 88			$ 847
Proceeds from sale of equity method investments and settlement of forward contract							$ 398
Balance, sold during period (in shares)				1.3
Outstanding vested equity interest percentage			5.00%				5.00%		10.00%
Cencora | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investments	$ 1,900
Outstanding vested equity interest percentage	5.00%
Cencora | Derivatives not designated as hedges:
Schedule of Equity Method Investments [Line Items]
Early settlement (in shares)			2.2	6.1			6.1
Early settlement value received (paid)			$ 103	$ (20)			$ (20)
Outstanding shares owned (in shares)				1.3
Pledged collateral (in shares)			10.4						20.0
Cencora | Derivatives not designated as hedges: | Subsequent Event
Schedule of Equity Method Investments [Line Items]
Early settlement (in shares)		2.4
Early settlement value received (paid)		$ 109
BrightSpring Health Services
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of equity method investments			$ 227				610
Gain on sale of equity method investments			$ 30				$ 322