Goodwill and intangibles - Composition of Finite-Lived Intangibles (Details) - USD ($) $ in Millions	Jul. 29, 2023	Jan. 28, 2023	Aug. 19, 2022	Jul. 30, 2022
Intangible assets, net:
Gross carrying amount	$ 15.8	$ 15.8		$ 15.8
Accumulated  amortization	(8.5)	(7.6)		(6.6)
Net carrying amount	7.3	8.2		9.2
Indefinite-lived intangible assets	399.2	399.2		303.6
Intangible assets, gross	415.0	415.0		319.4
Total intangible assets, net	406.5	407.4		312.8
Intangible liabilities, net
Gross carrying amount	(38.0)	(38.0)		(38.0)
Accumulated amortization	33.5	32.6		31.7
Total	$ (4.5)	$ (5.4)		$ (6.3)
Blue Nile
Indefinite-lived Intangible Assets [Line Items]
Intangible assets			$ 96.0
Blue Nile \| Trade names
Indefinite-lived Intangible Assets [Line Items]
Intangible assets			96.0
Blue Nile \| North America \| Trade names
Indefinite-lived Intangible Assets [Line Items]
Intangible assets			$ 96.0

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