Deferred Compensation (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jul. 31, 2023	Jul. 31, 2022	Jul. 31, 2023	Jul. 31, 2022	Jan. 31, 2023
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Costs to obtain a contract	$ 120,000,000		$ 120,000,000		$ 133,000,000
Amortization of costs to obtain a contract	33,000,000	$ 33,000,000	63,000,000	$ 67,000,000
Impairment loss	0	$ 0	0	$ 0
Rabbi Trust
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation liability	97,000,000		97,000,000		86,000,000
Deferred compensation liability, current	7,000,000		7,000,000		7,000,000
Deferred compensation liability, non-current	$ 90,000,000		$ 90,000,000		$ 79,000,000