Revenue recognition - ESP Deferred Revenue Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	May 02, 2020	May 04, 2019
Change in Contract with Customer, Liability [Roll Forward]
ESP deferred revenue, beginning of period	$ 997.7
ESP deferred revenue, end of period	991.0	$ 976.6
Extended Service Plan
Change in Contract with Customer, Liability [Roll Forward]
ESP deferred revenue, beginning of period	960.0	927.6
Plans sold	55.0	96.0
Revenue recognized	(54.0)	(92.3)
ESP deferred revenue, end of period	961.0	$ 931.3
Extended Service Plan and Voucher Promotions
Change in Contract with Customer, Liability [Roll Forward]
Revenue recognized	$ (44.5)