Deferred Compensation Additional Information (Details) - USD ($) $ in Millions	Oct. 31, 2015	Jan. 31, 2015
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Marketable securities	$ 1,500.0
Rabbi Trust Member
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Deferred compensation liability	44.0	$ 40.3
Deferred compensation liability current	5.2	5.3
Deferred compensation liability non-current	$ 38.8	$ 35.0