Other assets - Components of Other Assets (Details) - USD ($) $ in Millions	Apr. 30, 2016	Jan. 30, 2016	May. 02, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred ESP selling costs	$ 81.8	$ 79.4	$ 71.5
Investments	26.8	26.8	23.0
Other assets	48.6	48.4	37.6
Total other assets	157.2	154.6	132.1
Deferred costs related to the sale of the extended service plan	$ 27.5	$ 26.4	$ 26.8