Assets and liabilities at fair value - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
Jan. 31, 2025	Jan. 31, 2024	Jul. 31, 2024
Fair Value Disclosures [Abstract]
Hedged liability, fair value hedge	$ 150		$ 300
Repayments of debt	$ 2,100	$ 1,155

Amount of cash outflow for short-term and long-term debt. Excludes payment of lease obligation.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-15

Name:	us-gaap_RepaymentsOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration