Retirement plans - Components of UK Net Asset Recognized (Details) - USD ($) $ in Millions	Feb. 01, 2020	Feb. 02, 2019
Defined Benefit Plan Disclosure [Line Items]
Non-current assets		$ 30.6
Pension plan \| Foreign Plan
Defined Benefit Plan Disclosure [Line Items]
Non-current assets	$ 38.5	$ 30.6

Amount of asset, recognized in statement of financial position, for overfunded defined benefit pension and other postretirement plans.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant