Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Discrete tax items [Line Items]
Effective tax rate (percent)	25.40%	17.10%	21.30%	21.60%
Income tax expense (benefit)	$ 26.7	$ 19.6	$ 92.1	$ 105.2
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%)
True-up Of 2017 Tax Returns
Discrete tax items [Line Items]
Income tax expense (benefit)		$ (4.4)		$ (4.4)
Effective income tax rate reconciliation, deduction (percent)		(3.80%)		(0.90%)
Lapse In Statue Of Limitations
Discrete tax items [Line Items]
Income tax expense (benefit)				$ (8.0)
Effective income tax rate reconciliation, deduction (percent)				(1.60%)