Income taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 30, 2021	May 01, 2020
Income taxes
Reserves for uncertain tax benefits	$ 7.5
Interest accrued related to uncertain tax benefits	0.6
Potential penalties accrued related to uncertain tax benefits	0.0
Reserves for uncertain tax benefits included in noncurrent Other liabilities	8.1
Reserve for uncertain tax positions for which a reduction is reasonably possible in the next twelve months	3.4
Reserve for uncertain tax positions that would impact effective tax rate if recognized	$ 7.5
Effective income tax rates (as a percent)	22.00%	22.20%