Equity method investments - Narrative (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended			12 Months Ended
	Feb. 28, 2025	Feb. 29, 2024	Feb. 28, 2025	Feb. 29, 2024	Nov. 09, 2023	Aug. 31, 2024	Nov. 30, 2024
Schedule of Equity Method Investments [Line Items]
Gain on sale of equity method investments			$ 391	$ 758
Cencora | Walgreens Boots Alliance, Inc.
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)					12.6
Cencora
Schedule of Equity Method Investments [Line Items]
Balance, sold during period (in shares)	1.3
Proceeds from sale of equity method investments	$ 315	$ 992		1,200
Gain on sale of equity method investments	$ 204	$ 619		$ 758
Outstanding vested equity interest percentage	6.00%		6.00%			10.00%	10.00%
Cencora | Derivatives not designated as hedges:
Schedule of Equity Method Investments [Line Items]
Early settlement (in shares)	6.1		6.1
Outstanding shares owned (in shares)	1.3		1.3
Early settlement value	$ 20		$ 20
Pledged collateral (in shares)			12.6			20.0
BrightSpring Health Services
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of equity method investments	254		$ 383
Gain on sale of equity method investments	$ 155		$ 187
Outstanding vested equity interest percentage	6.00%		6.00%
Pretax gain			$ 157