Revenue recognition - ESP and Voucher Promotions (Details) - USD ($) $ in Millions	Oct. 31, 2020	Aug. 01, 2020	Feb. 01, 2020	Nov. 02, 2019	Aug. 03, 2019	Feb. 02, 2019
Disaggregation of Revenue [Line Items]
Total deferred revenue	$ 1,022.8		$ 997.7	$ 960.5
Current liabilities	258.5		266.2	267.3
Non-current liabilities	764.3		731.5	693.2
ESP deferred revenue
Disaggregation of Revenue [Line Items]
Total deferred revenue	983.2	$ 990.5	960.0	919.5	$ 930.2	$ 927.6
Voucher promotions and other
Disaggregation of Revenue [Line Items]
Total deferred revenue	$ 39.6		$ 37.7	$ 41.0