Accumulated other comprehensive income (loss) - Reclassifications out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Aug. 01, 2020	May 02, 2020	Aug. 03, 2019	May 04, 2019	Aug. 01, 2020	Aug. 03, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of sales	$ 663.9		$ 901.3		$ 1,312.2	$ 1,833.6
Interest expense, net	9.4		10.1		16.5	19.3
Other operating income, net	1.1		1.4		4.7	1.4
Other non-operating income, net	0.2		0.2		0.3	0.5
Income before income taxes	(98.9)		(32.3)		(405.5)	(43.8)
Income taxes	17.2		(3.8)		126.7	(2.3)
Net income (loss)	(81.7)	$ (197.1)	(36.1)	$ (10.0)	(278.8)	(46.1)
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income (loss)	(0.7)		0.3		(8.5)	0.1
Losses (gains) on cash flow hedges | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income (loss)	(0.8)		0.0		(8.9)	(0.4)
Losses (gains) on cash flow hedges, excluding dedesignated | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income taxes	(0.9)		0.0		(1.7)	(0.5)
Losses (gains) on cash flow hedges, excluding dedesignated | Reclassification out of Accumulated Other Comprehensive Income | Foreign currency contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of sales	0.0		(0.3)		0.0	(0.6)
Losses (gains) on cash flow hedges, excluding dedesignated | Reclassification out of Accumulated Other Comprehensive Income | Interest rate swaps
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense, net	0.0		0.0		0.0	(0.6)
Losses (gains) on cash flow hedges, excluding dedesignated | Reclassification out of Accumulated Other Comprehensive Income | Commodity contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of sales	(0.9)		0.3		(1.7)	0.7
Losses (gains) on dedesignating cash flow hedges | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income taxes	0.0		0.0		(9.9)	0.0
Income taxes	0.1		0.0		2.7	0.1
Losses (gains) on dedesignating cash flow hedges | Reclassification out of Accumulated Other Comprehensive Income | Foreign currency contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operating income, net	0.0		0.0		(0.6)	0.0
Losses (gains) on dedesignating cash flow hedges | Reclassification out of Accumulated Other Comprehensive Income | Commodity contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operating income, net	0.0		0.0		(9.3)	0.0
Defined benefit pension plan items | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income taxes	0.1		0.3		0.4	0.6
Income taxes	0.0		0.0		0.0	(0.1)
Net income (loss)	0.1		0.3		0.4	0.5
Actuarial gains (losses) | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other non-operating income, net	0.0		0.3		0.1	0.6
Prior service credits (costs) | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other non-operating income, net	$ 0.1		$ 0.0		$ 0.3	$ 0.0