Revenue recognition - ESP Deferred Revenue Rollforward (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Nov. 02, 2019	Oct. 31, 2020	Nov. 02, 2019
Change in Contract with Customer, Liability [Roll Forward]
ESP deferred revenue, beginning of period			$ 997.7
ESP deferred revenue, end of period	$ 1,022.8	$ 960.5	1,022.8	$ 960.5
Extended Service Plan
Change in Contract with Customer, Liability [Roll Forward]
ESP deferred revenue, beginning of period	990.5	930.2	960.0	927.6
Plans sold	83.8	78.0	193.2	264.5
Revenue recognized	(91.1)	(88.7)	(170.0)	(272.6)
ESP deferred revenue, end of period	983.2	$ 919.5	983.2	$ 919.5
Extended Service Plan and Voucher Promotions
Change in Contract with Customer, Liability [Roll Forward]
Revenue recognized	$ (61.6)		$ (115.8)