Income Tax (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 30, 2019	Apr. 30, 2018
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 32.8	$ 18.6
(Loss) income before income taxes	8.6	$ (63.8)
Unrecognized tax benefits	211.4
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact effective tax rate	194.6
Valuation allowance of deferred tax assets
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact effective tax rate	$ 16.9