Revenue and segment information - Identifiable Assets (Details) - USD ($) $ in Millions	Oct. 31, 2025	Jul. 31, 2025
Segment Reporting Information [Line Items]
Total assets	$ 17,694	$ 17,729
Total long-lived assets	1,886	1,846
United States
Segment Reporting Information [Line Items]
Total long-lived assets	1,836	1,795
Canada
Segment Reporting Information [Line Items]
Total long-lived assets	50	51
Operating Segments
Segment Reporting Information [Line Items]
Total assets	16,904	16,765
Corporate
Segment Reporting Information [Line Items]
Total assets	790	964
United States | Operating Segments
Segment Reporting Information [Line Items]
Total assets	15,914	15,757
Canada | Operating Segments
Segment Reporting Information [Line Items]
Total assets	$ 990	$ 1,008