Summary of significant accounting policies - Narrative (Details) - USD ($) $ in Millions	Apr. 30, 2025	Jul. 31, 2024
Accounting Policies [Abstract]
Supplier finance program, obligation, current	$ 46	$ 46

Amount of obligation for supplier finance program, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-3

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479468/405-50-50-4

Name:	us-gaap_SupplierFinanceProgramObligationCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant