Revenue recognition - ESP Deferred Revenue Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2021	Aug. 01, 2020	Jul. 31, 2021	Aug. 01, 2020
Change in Contract with Customer, Liability [Roll Forward]
ESP deferred revenue, beginning of period			$ 1,072.0
Plans sold			34.2	$ 32.9
ESP deferred revenue, end of period	$ 1,107.3	$ 1,030.2	1,107.3	1,030.2
Extended Service Plan
Change in Contract with Customer, Liability [Roll Forward]
ESP deferred revenue, beginning of period	1,049.4	961.0	1,028.9	960.0
Plans sold	118.6	55.7	242.7	109.4
Revenue recognized	104.2	26.2	207.8	78.9
ESP deferred revenue, end of period	1,063.8	990.5	1,063.8	990.5
Extended Service Plan and Voucher Promotions
Change in Contract with Customer, Liability [Roll Forward]
Revenue recognized	$ 63.9	$ 9.7	$ 136.5	$ 54.2