Earnings Per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net earnings	$ 95.1	$ 91.0	$ 288.3	$ 300.7
Weighted Average Number of Shares Outstanding, Basic	124.6	128.6	125.3	129.0
Incremental shares based upon the assumed exercise of stock options and unvested restricted stock units	0.3	0.5	0.4	0.5
Weighted Average Number of Shares Outstanding, Diluted	124.9	129.1	125.7	129.5
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1.2	0.7	1.4	0.7