Deferred Compensation (Details) - USD ($)	3 Months Ended
	Apr. 30, 2022	Apr. 30, 2021	Jan. 31, 2022
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Costs to obtain a contract	$ 125,000,000		$ 139,000,000
Amortization of costs to obtain a contract	34,000,000	$ 26,000,000
Impairment loss	0	$ 0
Rabbi Trust
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation liability	85,000,000		89,000,000
Deferred compensation liability, current	7,000,000		7,000,000
Deferred compensation liability, non-current	$ 78,000,000		$ 82,000,000