Restructuring plans - Schedule of Plan Liabilities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		45 Months Ended
	Oct. 30, 2021	Oct. 31, 2020	Oct. 30, 2021	Oct. 31, 2020	Oct. 30, 2021
Restructuring Reserve [Roll Forward]
Charged (credited) to expense	$ (1.7)	$ 3.6	$ (3.3)	$ 45.2
Signet Path to Brilliance
Restructuring Reserve [Roll Forward]
Beginning balance			10.2
Payments and other adjustments			(2.6)
Charged (credited) to expense	(1.7)	$ 5.6	(3.3)	$ 46.6	$ 249.3
Ending balance	4.3		4.3		4.3
Termination benefits | Signet Path to Brilliance
Restructuring Reserve [Roll Forward]
Beginning balance			2.1
Payments and other adjustments			(0.9)
Charged (credited) to expense	0.0		(1.1)		48.8
Ending balance	0.1		0.1		0.1
Store closure and other costs | Signet Path to Brilliance
Restructuring Reserve [Roll Forward]
Beginning balance			8.1
Payments and other adjustments			(1.7)
Charged (credited) to expense			(2.2)
Ending balance	$ 4.2		$ 4.2		$ 4.2