Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Millions	Jan. 31, 2017	Jan. 31, 2016
Deferred tax assets:
Inventory reserves	$ 24.8	$ 15.4
Accrued liabilities	12.9	15.7
Intangible assets	44.2	84.2
Net operating loss carryforward	81.2	59.5
Inventory capitalization	14.9	10.7
Other	19.9	5.2
Gross deferred tax assets	197.9	190.7
Deferred tax liabilities:
Intangible assets	(12.8)	(16.1)
Depreciation	(25.3)	(5.5)
Deferred tax liabilities	(38.1)	(21.6)
Net deferred tax asset (liability) before valuation allowance	159.8	169.1
Valuation allowance	(17.8)	(21.9)
Net deferred tax asset	$ 142.0	$ 147.2