Inventories - Rollforward of Inventory Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Feb. 01, 2020	Feb. 02, 2019	Feb. 03, 2018
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 95.3	$ 40.6	$ 43.2
Charged to profit	80.2	131.4	75.8
Utilization	(108.5)	(76.7)	(78.4)
Balance at end of period	67.0	95.3	$ 40.6
Signet Path to Brillance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	51.6
Charged to profit	9.2	62.2
Utilization	(40.0)	(10.6)
Balance at end of period	$ 20.8	$ 51.6