Income Tax (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 18.6	$ 8.2
(Loss) income before income taxes	(63.8)	$ (121.4)
Unrecognized tax benefits	341.3
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact effective tax rate	307.9
Valuation Allowance of Deferred Tax Assets
Income Tax Contingency [Line Items]
Unrecognized tax benefits that would impact effective tax rate	$ 33.4