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Restructuring plans - Restructuring and Related Costs (Details) - USD ($) $ in Millions	12 Months Ended			48 Months Ended
	Jan. 29, 2022	Jan. 30, 2021	Feb. 01, 2020	Jan. 29, 2022
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ (3.3)	$ 46.2	$ 69.9
Signet Path to Brillance
Restructuring Cost and Reserve [Line Items]
Restructuring charges	(3.3)	47.6	79.1	$ 249.3
Signet Path to Brillance \| Cost of sales
Restructuring Cost and Reserve [Line Items]
Inventory charges	0.0	1.4	9.2
Signet Path to Brillance \| Restructuring charges
Restructuring Cost and Reserve [Line Items]
Other Plan related expenses	(3.3)	46.2	69.9
Inventory charges \| Signet Path to Brillance
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.0	1.4	9.2	72.8
Termination benefits \| Signet Path to Brillance
Restructuring Cost and Reserve [Line Items]
Restructuring charges	(1.1)	24.1	16.1	48.8
Store closure and other costs \| Signet Path to Brillance
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ (2.2)	$ 22.1	$ 53.8	$ 127.7