Retirement plans - Fair Value Measurements of Plan Assets (Details) - USD ($) $ in Millions	Feb. 01, 2020	Feb. 02, 2019	Feb. 03, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 27.5	$ 33.9
Quoted prices in active markets for identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21.0	26.9
Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.5	7.0
Foreign Plan | Pension plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	281.9	245.5	$ 272.2
Foreign Plan | Pension plan | Quoted prices in active markets for identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	193.8	45.5
Foreign Plan | Pension plan | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	63.9	169.0
Foreign Plan | Pension plan | Significant unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Foreign Plan | Pension plan | Diversified equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.1	19.4
Foreign Plan | Pension plan | Diversified equity securities | Quoted prices in active markets for identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Foreign Plan | Pension plan | Diversified equity securities | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.1	19.4
Foreign Plan | Pension plan | Diversified growth funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49.8	66.4
Foreign Plan | Pension plan | Diversified growth funds | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17.8	17.4
Foreign Plan | Pension plan | Diversified growth funds | Quoted prices in active markets for identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	49.8	43.6
Foreign Plan | Pension plan | Diversified growth funds | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	22.8
Foreign Plan | Pension plan | Fixed income – government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	139.7	80.6
Foreign Plan | Pension plan | Fixed income – government bonds | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	80.6
Foreign Plan | Pension plan | Corporate bonds and notes
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48.8	46.2
Foreign Plan | Pension plan | Corporate bonds and notes | Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48.8	46.2
Foreign Plan | Pension plan | Property | NAV
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.4	13.6
Foreign Plan | Pension plan | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4.3	1.9
Foreign Plan | Pension plan | Cash | Quoted prices in active markets for identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 4.3	$ 1.9