Other assets - Components of Other Assets (Detail) - USD ($) $ in Millions	Aug. 01, 2015	Jan. 31, 2015	Aug. 02, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred extended service plan costs	$ 75.2	$ 69.7	$ 64.5
Investments	23.2	25.2	22.3
Other assets	47.0	45.1	46.2
Total other assets	145.4	140.0	133.0
Deferred costs related to the sale of the extended service plan	$ 23.9	$ 24.9	$ 22.9