Summary of significant accounting policies - Useful Life of PPE (Details)	Jul. 31, 2024
Owned buildings | Minimum
Property, Plant and Equipment [Line Items]
Useful life (in years)	20 years
Owned buildings | Maximum
Property, Plant and Equipment [Line Items]
Useful life (in years)	50 years
Plant and machinery
Property, Plant and Equipment [Line Items]
Useful life (in years)	10 years
Computer hardware | Minimum
Property, Plant and Equipment [Line Items]
Useful life (in years)	3 years
Computer hardware | Maximum
Property, Plant and Equipment [Line Items]
Useful life (in years)	5 years
Furniture, fixtures, equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful life (in years)	5 years
Furniture, fixtures, equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful life (in years)	7 years
Vehicles
Property, Plant and Equipment [Line Items]
Useful life (in years)	4 years