New Accounting Standards (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jul. 31, 2017	Jul. 31, 2017	Jul. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Payments Related to Tax Withholding for Share-based Compensation		$ 7.2	$ 2.6
ASU 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess Tax Benefits Recognized	$ 0.6	$ 3.0
Payments Related to Tax Withholding for Share-based Compensation			2.6
Excess Tax Benefit From Share-Based Compensation, Amount Reclassified to Operating Activities from Financing Activites			$ 0.5