Retirement Benefit Plans - Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Tax, after Reclassification Adjustment, Attributable to Parent [Abstract]
Prior service credit for period	$ 0.2	$ 0.0	$ (2.2)
Net (gain) loss for period	(2.5)	7.2	9.1
Effect of settlement	(1.9)	(1.2)	0.0
Effect of curtailment	(0.2)	0.0	0.0
Amortization of prior service credit	0.3	0.3	0.1
Amortization of net loss	(1.2)	(1.5)	(1.4)
Other comprehensive (income) loss	$ (5.3)	$ 4.8	$ 5.6