Other assets - Components of Other Assets (Details) - USD ($) $ in Millions	Oct. 29, 2016	Jan. 30, 2016	Oct. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred ESP selling costs	$ 81.8	$ 79.4	$ 74.6
Investments	27.5	26.8	25.0
Other assets	48.2	48.4	36.8
Total other assets	157.5	154.6	136.4
Deferred costs related to the sale of the extended service plan	$ 27.6	$ 26.4	$ 24.0