Restructuring plans - Schedule of Plan Liabilities (Details) - USD ($) $ in Millions	12 Months Ended			48 Months Ended
	Jan. 29, 2022	Jan. 30, 2021	Feb. 01, 2020	Jan. 29, 2022
Restructuring Reserve [Roll Forward]
Charged to expense	$ (3.3)	$ 46.2	$ 69.9
Signet Path to Brillance
Restructuring Reserve [Roll Forward]
Beginning balance	10.2	12.4	12.6
Payments and other adjustments	(2.9)	(49.8)	(79.3)
Charged to expense	(3.3)	47.6	79.1	$ 249.3
Ending balance	4.0	10.2	12.4	4.0
Termination benefits | Signet Path to Brillance
Restructuring Reserve [Roll Forward]
Beginning balance	2.1	2.0	0.0
Payments and other adjustments	(1.0)	(24.0)	(14.1)
Charged to expense	(1.1)	24.1	16.1	48.8
Ending balance	0.0	2.1	2.0	0.0
Store closure and other costs | Signet Path to Brillance
Restructuring Reserve [Roll Forward]
Beginning balance	8.1	10.4	12.6
Payments and other adjustments	(1.9)	(25.8)	(65.2)
Charged to expense	(2.2)	23.5	63.0
Ending balance	$ 4.0	$ 8.1	$ 10.4	$ 4.0