Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Discrete tax items [Line Items]
Effective tax rate (percent)	19.90%	25.40%	20.30%	21.30%
Income tax expense (benefit)	$ 29.6	$ 26.7	$ 21.9	$ 92.1
Change In Estimated 2019 Foreign Derived Intangible Income
Discrete tax items [Line Items]
Income tax expense (benefit)		$ 5.8		$ 5.8
Effective income tax rate reconciliation, deduction (percent)		5.50%		1.30%
Change In Estimated 2018 Foreign Derived Intangible Income
Discrete tax items [Line Items]
Income tax expense (benefit)				$ (7.5)
Effective income tax rate reconciliation, deduction (percent)				(1.70%)