Revenue and segment information - Identifiable Assets (Details) - USD ($) $ in Millions	Jul. 31, 2024	Jul. 31, 2023
Segment Reporting Information [Line Items]
Total assets	$ 16,572	$ 15,994
Corporate
Segment Reporting Information [Line Items]
Total assets	879	1,032
United States | Operating Segments
Segment Reporting Information [Line Items]
Total assets	14,795	14,167
Canada | Operating Segments
Segment Reporting Information [Line Items]
Total assets	$ 898	$ 795