Segment information - Summary of Activity by Segment (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2018	Aug. 04, 2018	Jul. 29, 2017	Aug. 04, 2018	Jul. 29, 2017	Feb. 03, 2018
Segment Reporting Information [Line Items]
Sales		$ 1,420.1	$ 1,399.6	$ 2,900.7	$ 2,803.0
Operating income (loss)		(58.1)	135.6	(632.3)	250.9
Total assets		4,740.8	6,313.8	4,740.8	6,313.8	$ 5,839.6
Proceeds from sale of in-house finance receivables	$ 445.5			445.5	0.0
Goodwill and intangible impairments		0.0	0.0	448.7	0.0
Restructuring costs		19.6	0.0	26.1	0.0
North America
Segment Reporting Information [Line Items]
Sales		1,286.7	1,262.2	2,634.5	2,536.6
Operating income (loss)		(4.2)	161.6	(541.5)	296.4
Total assets		4,171.9	5,826.3	4,171.9	5,826.3	5,309.0
Goodwill and intangible impairments				448.7
Transaction-related costs		19.4		160.4
Restructuring costs		53.7		53.7
International
Segment Reporting Information [Line Items]
Sales		131.5	131.9	260.2	254.4
Operating income (loss)		(6.1)	2.3	(13.7)	(0.2)
Total assets		366.6	384.8	366.6	384.8	420.3
Inventory charges(1)		3.8
Other
Segment Reporting Information [Line Items]
Sales		1.9	5.5	6.0	12.0
Operating income (loss)		(47.8)	(28.3)	(77.1)	(45.3)
Total assets		202.3	$ 102.7	202.3	$ 102.7	$ 110.3
Transaction-related costs		4.5		6.6
Restructuring costs		$ 25.3		$ 31.8