Net Earnings Per Common Share (Computations of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
Net Earnings Per Common Share
Net earnings	$ 31.7	$ 18.4
Basic weighted average common shares (in millions)	50.1	51.1
Effect of dilutive securities - dilutive securities	0.8	0.7
Diluted weighted average common shares (in millions)	50.9	51.8
Basic net earnings per common share	$ 0.63	$ 0.36
Diluted net earnings per common share	$ 0.62	$ 0.36