Deferred Compensation - Additional Information (Details) - USD ($)	3 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Jan. 31, 2021
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Costs to obtain a contract	$ 118,100,000		$ 120,900,000
Amortization of costs to obtain a contract	25,800,000	$ 22,800,000
Impairment loss	0	$ 0
Prepaid expenses and other current assets
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation plan assets	7,600,000		7,300,000
Long-term other assets
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation plan assets	83,600,000		73,700,000
Rabbi Trust
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation plan assets	91,200,000		81,000,000.0
Deferred compensation liability	91,200,000		81,000,000.0
Deferred compensation liability, current	7,600,000		7,300,000
Deferred compensation liability, non-current	$ 83,600,000		$ 73,700,000