Receivables and Revenue Recognition - Receivables (Details) - USD ($) $ in Millions	Apr. 30, 2018	Jan. 31, 2018	Apr. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Consumer Credit Card Financing Receivables	$ 72.8		$ 76.0
Consumer Credit Card Financing Receivables Percentage Current	97.00%		97.00%
Consumer Credit Card Financing Receivable Allowance For Credit Losses	$ 1.3		$ 1.1
Allowance for Doubtful Accounts Receivable, Current	29.9	$ 17.2	12.7
Prepaid expenses and other current assets	223.0	$ 207.4	$ 204.0
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Prepaid expenses and other current assets	$ 13.3