Restructuring plans - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		45 Months Ended
	Oct. 30, 2021	Oct. 31, 2020	May 05, 2018	Oct. 30, 2021	Oct. 31, 2020	Oct. 30, 2021	Jan. 30, 2021
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 1.7	$ (3.6)		$ 3.3	$ (45.2)
Signet Path to Brilliance
Restructuring Cost and Reserve [Line Items]
Restructuring plan, length			3 years
Restructuring charges	1.7	$ (5.6)		3.3	$ (46.6)	$ (249.3)
Restructuring reserve	4.3			4.3		4.3	$ 10.2
Signet Path to Brilliance | Accrued expenses and other current liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	2.3			2.3		2.3
Signet Path to Brilliance | Other noncurrent liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring reserve	$ 2.0			$ 2.0		$ 2.0