Stockholders' Equity Share Repurchase Table (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Equity [Abstract]
Cost of repurchases	$ 71.8	$ 22.7	$ 149.9	$ 55.8
Purchase and retirement of Common Stock, Shares	1.1	0.3	2.3	0.6
Average cost per share	$ 62.71	$ 90.43	$ 64.62	$ 88.46