Restructuring plans - Restructuring and Related Costs (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 Cost and Reserve [Line Items]
Total Signet Path to Brilliance Plan expenses	$ (1.7)	$ 3.6	$ (3.3)	$ 45.2
Cost of sales
Restructuring Cost and Reserve [Line Items]
Inventory charges			0.0	1.4
Restructuring Charges
Restructuring Cost and Reserve [Line Items]
Other Plan related expenses			(3.3)	45.2
Signet Path to Brilliance
Restructuring Cost and Reserve [Line Items]
Total Signet Path to Brilliance Plan expenses	(1.7)	5.6	(3.3)	$ 46.6	$ 249.3
Signet Path to Brilliance | Cost of sales
Restructuring Cost and Reserve [Line Items]
Inventory charges	0.0	2.0
Signet Path to Brilliance | Restructuring Charges
Restructuring Cost and Reserve [Line Items]
Other Plan related expenses	(1.7)	$ 3.6
Inventory charges | Signet Path to Brilliance
Restructuring Cost and Reserve [Line Items]
Total Signet Path to Brilliance Plan expenses	0.0		0.0		72.8
Termination benefits | Signet Path to Brilliance
Restructuring Cost and Reserve [Line Items]
Total Signet Path to Brilliance Plan expenses	0.0		(1.1)		48.8
Store closure and other costs | Signet Path to Brilliance
Restructuring Cost and Reserve [Line Items]
Total Signet Path to Brilliance Plan expenses	$ (1.7)		$ (2.2)		$ 127.7