Deferred Compensation (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jul. 31, 2021	Jul. 31, 2020	Jul. 31, 2021	Jul. 31, 2020	Jan. 31, 2021
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Costs to obtain a contract	$ 114,000,000		$ 114,000,000		$ 120,900,000
Amortization of costs to obtain a contract	28,200,000	$ 23,600,000	54,000,000	$ 46,400,000
Impairment loss	0	$ 0	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	7,700,000		7,700,000		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	85,300,000		85,300,000		73,700,000
Rabbi Trust
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation plan assets	93,000,000		93,000,000		81,000,000
Deferred compensation liability	93,000,000		93,000,000		81,000,000
Deferred compensation liability, current	7,700,000		7,700,000		7,300,000
Deferred compensation liability, non-current	$ 85,300,000		$ 85,300,000		$ 73,700,000