Subsequent events (Details) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	6 Months Ended
	Mar. 31, 2025 USD ($) shares	Feb. 28, 2025 USD ($) shares	Feb. 29, 2024 USD ($)	Mar. 06, 2025 USD ($) right $ / shares
Subsequent Event [Line Items]
Gain (loss) on variable prepaid forward contracts		$ 777	$ (888)
Cencora | Derivatives not designated as hedges:
Subsequent Event [Line Items]
Early settlement (in shares) | shares		6.1
Early settlement value		$ 20
Subsequent Event | Cencora | Derivatives not designated as hedges:
Subsequent Event [Line Items]
Early settlement (in shares) | shares	2.2
Early settlement value	$ 103
Gain (loss) on variable prepaid forward contracts	$ 378
Subsequent Event | Stefano Pessina | Walgreens Boots Alliance, Inc.
Subsequent Event [Line Items]
Equity ownership, excluding consolidated entity and equity method investee, percentage				17.00%
Subsequent Event | Walgreens Boots Alliance, Inc. | Blazing Star Parent, LLC
Subsequent Event [Line Items]
Business acquisition, share price (in USD per share) | $ / shares				$ 11.45
Divested asset proceed right | right				1
Net proceeds acquired, percentage				70.00%
Divested asset proceed right price | $ / shares				$ 3.00
Termination fee payable by acquirer				$ 560
Documented out-of-pocket expenses				30
Subsequent Event | Walgreens Boots Alliance, Inc. | Blazing Star Parent, LLC | Minimum
Subsequent Event [Line Items]
Termination fee payable by acquirer, acquirer terminated				158
Subsequent Event | Walgreens Boots Alliance, Inc. | Blazing Star Parent, LLC | Maximum
Subsequent Event [Line Items]
Termination fee payable by acquirer, acquirer terminated				$ 316