Summary of Significant Accounting Policies New Accounting Standards (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Earnings from operations before income taxes	$ 760.5	$ 676.6	$ 709.9
Cost of sales (reclassified from ASU implementation)	1,565.1	1,511.5	1,613.6
Selling, general and administrative expenses (reclassified from ASU implementation)	1,810.2	1,769.1	1,731.2
Payments Related to Tax Withholding for Share-based Compensation	(8.7)	(2.9)	(1.6)
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effective tax rate reconciliation, based based compensation, excess tax benefit	6.8
Excess tax benefit from share-based compensation, operating activities		0.7	$ 2.2
Accounting Standards Update 2017-07 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Earnings from operations before income taxes	14.9	25.2
Cost of sales (reclassified from ASU implementation)	(6.0)	(8.7)
Selling, general and administrative expenses (reclassified from ASU implementation)	$ (8.9)	$ (16.5)