Stockholders' Equity Share Repurchase Table (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Equity [Abstract]
Cost of repurchases	$ 27.7	$ 30.8	$ 60.2	$ 180.7
Purchase and retirement of Common Stock, Shares	0.3	0.5	0.7	2.8
Average cost per share	$ 92.31	$ 67.72	$ 92.16	$ 65.13