Accumulated other comprehensive income (loss) - Reclassifications out of AOCI (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Feb. 01, 2020	Nov. 02, 2019	Aug. 03, 2019	May 04, 2019	Feb. 02, 2019	Nov. 03, 2018	Aug. 04, 2018	May 05, 2018	Feb. 01, 2020	Feb. 02, 2019	Feb. 03, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of sales									$ (3,904.2)	$ (4,024.1)	$ (4,063.0)
Interest expense, net									(35.6)	(39.7)	(52.7)
Other non-operating income, net									7.0	1.7	0.0
Other operating income (loss)									(29.6)	26.2	260.8
Total before income tax									129.7	(802.6)	527.2
Income taxes									(24.2)	145.2	(7.9)
Net income (loss)	$ 178.8	$ (43.7)	$ (44.3)	$ (18.2)	$ (116.2)	$ (38.1)	$ (31.2)	$ (504.8)	105.5	(657.4)	519.3
Reclassification out of AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net income (loss)									(0.7)	(0.8)	(5.4)
Reclassification out of AOCI | Gains (losses) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total before income tax									(3.4)	(2.1)	(4.6)
Income taxes									0.7	0.6	1.1
Net income (loss)									(2.7)	(1.5)	(3.5)
Reclassification out of AOCI | Accumulated defined benefit plans adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total before income tax									1.2	0.9	(2.3)
Income taxes									(0.2)	(0.2)	0.4
Net income (loss)									1.0	0.7	(1.9)
Reclassification out of AOCI | Actuarial gains (losses)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other non-operating income, net									1.2	0.9	2.8
Reclassification out of AOCI | Prior service credits (costs)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other non-operating income, net									0.0	0.0	(1.4)
Reclassification out of AOCI | Net curtailment gain and settlement loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other non-operating income, net									0.0	0.0	(3.7)
Reclassification out of AOCI | Available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operating income (loss)									1.0	0.0	0.0
Income taxes									0.0	0.0	0.0
Net income (loss)									1.0	0.0	0.0
Reclassification out of AOCI | Foreign currency contracts | Gains (losses) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of sales									(1.1)	0.7	(3.2)
Reclassification out of AOCI | Interest rate swaps | Gains (losses) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense, net									(0.6)	(1.9)	0.3
Reclassification out of AOCI | Commodity contracts | Gains (losses) on cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of sales									$ (1.7)	$ (0.9)	$ (1.7)