Deferred Compensation (Additional Information) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Jan. 31, 2020
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Marketable securities	$ 78,500,000		$ 78,500,000		$ 69,000,000.0
Costs to obtain a contract	89,400,000		89,400,000		98,800,000
Amortization of costs to obtain a contract	23,800,000	$ 25,200,000	70,200,000	$ 75,400,000
Impairment loss			0	$ 0
Rabbi Trust
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation liability	74,500,000		74,500,000		69,000,000.0
Deferred compensation liability, current	5,300,000		5,300,000		5,300,000
Deferred compensation liability, non-current	$ 69,200,000		$ 69,200,000		$ 63,700,000