Accumulated other comprehensive loss - Change in AOCI (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jan. 31, 2025	Oct. 31, 2024	Jan. 31, 2024	Oct. 31, 2023	Jan. 31, 2025	Jan. 31, 2024
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ 5,616			$ 5,616
Other comprehensive (loss) income before reclassifications	$ (33)	(5)	$ 23	$ (37)
Amounts reclassified from accumulated other comprehensive loss	2	3	2	3
Total other comprehensive (loss) income, net of tax	(31)	(2)	25	(34)	(33)	$ (9)
Ending balance	5,489		5,418		5,489	5,418
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(933)	(931)	(922)	(888)	(931)	(888)
Total other comprehensive (loss) income, net of tax	(31)		25		(33)	(9)
Ending balance	(964)	(933)	(897)	(922)	(964)	(897)
Foreign currency translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(468)	(461)	(464)	(429)	(461)	(429)
Other comprehensive (loss) income before reclassifications	(32)	(7)	21	(35)
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Total other comprehensive (loss) income, net of tax	(32)	(7)	21	(35)
Ending balance	(500)	(468)	(443)	(464)	(500)	(443)
Pensions
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(465)	(470)	(458)	(459)	(470)	(459)
Other comprehensive (loss) income before reclassifications	(1)	2	2	(2)
Amounts reclassified from accumulated other comprehensive loss	2	3	2	3
Total other comprehensive (loss) income, net of tax	1	5	4	1
Ending balance	$ (464)	$ (465)	$ (454)	$ (458)	$ (464)	$ (454)