Retirement Benefit Plans - Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax, Portion Attributable to Parent [Abstract]
Net loss (gain) for period	$ 18.4	$ (3.9)	$ 6.3
Amortization of prior service credit	0.1	0.1	0.1
Amortization of net loss	(0.6)	(1.0)	(0.7)
Other comprehensive loss (income)	$ 17.9	$ (4.8)	$ 5.7