Share-based compensation - Schedule of Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jan. 31, 2025	Jan. 31, 2024	Jan. 31, 2025	Jan. 31, 2024
Share-Based Payment Arrangement [Abstract]
Share-based compensation expense (within SG&A)	$ 2	$ 11	$ 13	$ 24
Income tax benefit	$ 0	$ 3	$ 3	$ 6