Restructuring and impairment expenses - Narrative (Details) - USD ($)	12 Months Ended
	Jul. 31, 2025	Jul. 31, 2024	Jul. 31, 2023
Restructuring Cost and Reserve [Line Items]
Severance costs	$ 45,000,000
Non-cash branch and facility costs	15,000,000
Impairment expenses	0	$ 0	$ 107,000,000
Software
Restructuring Cost and Reserve [Line Items]
Impairment, Intangible Asset, Finite-Lived, Statement of Income or Comprehensive Income [Extensible Enumeration]			Restructuring Costs and Asset Impairment Charges
Impairment charges			$ 107,000,000
Business restructuring expenses
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 73,000,000	$ 0	$ 18,000,000