Assets and liabilities at fair value - Narrative (Details) - USD ($) $ in Millions	Oct. 31, 2025	Jul. 31, 2025
Fair Value Disclosures [Abstract]
Hedged liability, fair value hedge	$ 150	$ 150

Amount of liability hedged in fair value hedging relationship.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4EE
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4EE

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