Income Tax (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended	9 Months Ended
	Oct. 31, 2015	Jul. 31, 2015	Oct. 31, 2014	Jul. 31, 2015	Oct. 31, 2015	Oct. 31, 2014	Jan. 31, 2015
Income Tax Disclosure [Abstract]
Income tax expense	$ 21.3	$ 269.5	$ 0.9	$ 272.2	$ 293.5	$ 19.8
(Loss) income before income taxes	(22.5)		$ 11.6		0.2	$ 90.1
Deferred tax assets valuation allowance	312.3	$ 230.8		$ 230.8	312.3		$ 26.7
Unrecognized tax benefits	254.0				254.0
Unrecognized tax benefits that would impact effective tax rate	$ 236.6				$ 236.6