Goodwill and intangibles - Composition of Finite-Lived Intangibles (Details) - USD ($) $ in Millions	Nov. 03, 2018	Feb. 03, 2018	Oct. 28, 2017
Intangible assets, net:
Gross carrying amount	$ 53.3	$ 49.8	$ 49.4
Accumulated amortization	(49.3)	(46.7)	(45.1)
Net carrying amount	4.0	3.1	4.3
Accumulated amortization	(139.7)
Intangible assets, gross	529.2	528.2	455.5
Accumulated amortization, net	(49.3)	(46.7)	(45.1)
Total intangible assets, net	340.2	481.5	410.4
Definite-lived intangible liabilities:
Gross carrying amount	(113.9)	(114.5)	(114.1)
Accumulated amortization	90.7	85.2	83.0
Total	(23.2)	(29.3)	(31.1)
Trade names
Intangible assets, net:
Indefinite-lived intangible assets, gross	475.9	478.4	406.1
Accumulated amortization	(139.7)
Indefinite-lived intangible assets	$ 336.2	$ 478.4	$ 406.1