Income taxes - Summary of Income and Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Feb. 01, 2020	Feb. 02, 2019	Feb. 03, 2018
Income (loss) before income taxes:
– US	$ 32.3	$ (1,135.8)	$ 202.2
– Foreign	97.4	333.2	325.0
Income (loss) before income taxes	129.7	(802.6)	527.2
Current taxation:
– US	3.0	(55.2)	35.9
– Foreign	1.9	15.8	6.1
Deferred taxation:
– US	17.0	(85.8)	(34.8)
– Foreign	2.3	(20.0)	0.7
Total income tax expense (benefit)	$ 24.2	$ (145.2)	$ 7.9