Income Tax (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Income Tax Contingency [Line Items]
Provision for income taxes	$ 24.0	$ 32.8
(Loss) income before income taxes	90.5	$ 8.6
Unrecognized tax benefits	218.6
Unrecognized tax benefits that would impact effective tax rate	201.7
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact effective tax rate	$ 16.9