New accounting pronouncements - Narrative (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Feb. 02, 2019	Nov. 03, 2018	Aug. 04, 2018	May 05, 2018	Feb. 03, 2018	Oct. 28, 2017	Jul. 29, 2017	Apr. 29, 2017	Feb. 02, 2019	Feb. 03, 2018	Jan. 28, 2017	Feb. 01, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Sales		$ 2,154.7	$ 1,191.7	$ 1,420.1	$ 1,480.6	$ 2,293.1	$ 1,156.9	$ 1,399.6	$ 1,403.4	$ 6,247.1	$ 6,253.0	$ 6,408.4
Impact from adoption of new accounting pronouncements	[1]					$ (16.5)					$ (16.5)
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Sales										111.2
Impact from adoption of new accounting pronouncements		$ (16.5)								$ (16.5)
Minimum | Scenario, Forecast | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, right-of-use asset													$ 1,800.0
Operating lease, liability													1,800.0
Maximum | Scenario, Forecast | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, right-of-use asset													2,200.0
Operating lease, liability													$ 2,200.0

[1] Adjustments reflect reclassifications to retained earnings related to 1) deferred costs associated with the sale of extended service plans due to the adoption of ASU 2014-09 and 2) unrealized gains related to the Company’s equity security investments as of February 3, 2018 from AOCI associated with the adoption of ASU 2016-01.