Inventories - Rollforward of Inventory Reserves (Details) - USD ($) $ in Millions	12 Months Ended
	Feb. 02, 2019	Feb. 03, 2018	Jan. 28, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 40.6	$ 43.2	$ 43.2
Charged to profit	131.4	75.8	57.3
Utilization	(76.7)	(78.4)	(57.3)
Balance at end of period	95.3	$ 40.6	$ 43.2
Signet Path to Brillance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Charged to profit	62.2
Utilization	(10.6)
Balance at end of period	$ 51.6