Employee Benefit Plans Amounts Recognized in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	Jan. 31, 2018	Jan. 31, 2017
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	$ 116.5	$ 161.8
Prior service cost (credit)	0.6	0.8
Total before tax	117.1	162.6
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	1.3	(0.1)
Prior service cost (credit)	(1.7)	(2.4)
Total before tax	$ (0.4)	$ (2.5)