Inventories - Rollforward of Inventory Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 30, 2021	Feb. 01, 2020	Feb. 02, 2019
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 67.0	$ 95.3	$ 40.6
Charged to profit	78.1	80.2	131.4
Utilization	(92.2)	(108.5)	(76.7)
Balance at end of period	52.9	67.0	95.3
Signet Path to Brillance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	20.8	51.6
Charged to profit	1.4	9.2	62.2
Utilization	(20.0)	(40.0)	(10.6)
Balance at end of period	$ 2.2	$ 20.8	$ 51.6