Retirement plans - Components of Net Periodic Pension Cost (Details) - Pension plan - Foreign Plan - USD ($) $ in Millions	12 Months Ended
	Feb. 01, 2020	Feb. 02, 2019	Feb. 03, 2018
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ (0.7)	$ (0.9)	$ (2.1)
Interest cost	(5.5)	(5.8)	(6.1)
Expected return on UK Plan assets	7.8	8.4	9.4
Amortization of unrecognized actuarial losses	(1.2)	(0.9)	(2.8)
Amortization of unrecognized net prior service credits	0.0	0.0	1.4
Net curtailment gain and settlement loss	0.0	0.0	3.7
Total net periodic benefit (cost) income	0.4	0.8	3.5
Other changes in assets and benefit obligations recognized in OCI	1.7	(11.3)	(2.9)
Total recognized in net periodic pension benefit (cost) and OCI	$ 2.1	$ (10.5)	$ 0.6