Condensed consolidating financial information - Condensed consolidating statement of operations (Details) - USD ($) $ in Millions	3 Months Ended							9 Months Ended
	Nov. 02, 2019	Aug. 03, 2019	May 04, 2019	Feb. 02, 2019	Nov. 03, 2018	Aug. 04, 2018	May 05, 2018	Nov. 02, 2019	Nov. 03, 2018
Condensed Income Statements, Captions [Line Items]
Sales	$ 1,187.7				$ 1,191.7			$ 3,983.8	$ 4,092.4
Cost of sales	(818.6)				(820.5)			(2,652.2)	(2,746.2)
Restructuring charges - cost of sales	(1.4)				0.0			(5.8)	(63.2)
Gross margin	367.7				371.2			1,325.8	1,283.0
Selling, general and administrative expenses	(398.4)				(410.3)			(1,285.0)	(1,337.9)
Credit transaction, net	0.0				(0.4)			0.0	(167.4)
Restructuring charges	(9.2)				(9.5)			(59.4)	(35.6)
Goodwill and intangible impairments	0.0			$ (286.7)	0.0			(47.7)	(448.7)
Other operating income, net	0.0				0.2			1.4	25.5
Operating income (loss)	(39.9)				(48.8)			(64.9)	(681.1)
Intra-entity interest income (expense)	0.0				0.0			0.0	0.0
Interest expense, net	(8.6)				(10.6)			(27.9)	(28.9)
Other non-operating income	7.0				0.3			7.5	1.4
Income (loss) before income taxes	(41.5)				(59.1)			(85.3)	(708.6)
Income tax benefit	6.0				29.2			3.7	159.1
Equity in income of subsidiaries	0.0				0.0			0.0	0.0
Net income (loss)	(35.5)	$ (36.1)	$ (10.0)		(29.9)	$ (23.0)	$ (496.6)	(81.6)	(549.5)
Dividends on redeemable convertible preferred shares	(8.2)				(8.2)			(24.6)	(24.6)
Net income (loss) attributable to common shareholders	(43.7)				(38.1)			(106.2)	(574.1)
Consolidation, Eliminations
Condensed Income Statements, Captions [Line Items]
Sales	0.0				0.0			0.0	0.0
Cost of sales	0.0				0.0			0.0	0.0
Restructuring charges - cost of sales	0.0							0.0
Gross margin	0.0				0.0			0.0	0.0
Selling, general and administrative expenses	0.0				0.0			0.0	0.0
Credit transaction, net					0.0				0.0
Restructuring charges	0.0				0.0			0.0	0.0
Goodwill and intangible impairments								0.0	0.0
Other operating income, net	0.0				0.0			0.0	0.0
Operating income (loss)	0.0				0.0			0.0	0.0
Intra-entity interest income (expense)	0.0				0.0			0.0	0.0
Interest expense, net	0.0				0.0			0.0	0.0
Other non-operating income	0.0				0.0			0.0	0.0
Income (loss) before income taxes	0.0				0.0			0.0	0.0
Income tax benefit	0.0				0.0			0.0	0.0
Equity in income of subsidiaries	216.2				189.9			579.5	2,268.3
Net income (loss)	216.2				189.9			579.5	2,268.3
Dividends on redeemable convertible preferred shares	0.0				0.0			0.0	0.0
Net income (loss) attributable to common shareholders	216.2				189.9			579.5	2,268.3
Signet Jewelers Limited | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	0.0				0.0			0.0	0.0
Cost of sales	0.0				0.0			0.0	0.0
Restructuring charges - cost of sales	0.0							0.0
Gross margin	0.0				0.0			0.0	0.0
Selling, general and administrative expenses	(0.2)				(0.2)			(0.4)	(0.7)
Credit transaction, net					0.0				0.0
Restructuring charges	0.0				0.0			0.0	0.0
Goodwill and intangible impairments								0.0	0.0
Other operating income, net	0.0				0.0			0.0	(0.1)
Operating income (loss)	(0.2)				(0.2)			(0.4)	(0.8)
Intra-entity interest income (expense)	(0.4)				(1.0)			(1.6)	(3.4)
Interest expense, net	0.0				0.0			0.0	0.0
Other non-operating income	0.0				0.0			0.0	0.0
Income (loss) before income taxes	(0.6)				(1.2)			(2.0)	(4.2)
Income tax benefit	0.0				0.0			0.0	0.0
Equity in income of subsidiaries	(34.9)				(28.7)			(79.6)	(545.3)
Net income (loss)	(35.5)				(29.9)			(81.6)	(549.5)
Dividends on redeemable convertible preferred shares	(8.2)				(8.2)			(24.6)	(24.6)
Net income (loss) attributable to common shareholders	(43.7)				(38.1)			(106.2)	(574.1)
Signet UK Finance plc | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	0.0				0.0			0.0	0.0
Cost of sales	0.0				0.0			0.0	0.0
Restructuring charges - cost of sales	0.0							0.0
Gross margin	0.0				0.0			0.0	0.0
Selling, general and administrative expenses	0.0				0.0			0.0	0.0
Credit transaction, net					0.0				0.0
Restructuring charges	0.0				0.0			0.0	0.0
Goodwill and intangible impairments								0.0	0.0
Other operating income, net	0.0				0.0			0.0	0.0
Operating income (loss)	0.0				0.0			0.0	0.0
Intra-entity interest income (expense)	3.7				4.7			13.1	14.1
Interest expense, net	(3.8)				(5.1)			(13.7)	(14.9)
Other non-operating income	8.8				0.0			8.8	0.0
Income (loss) before income taxes	8.7				(0.4)			8.2	(0.8)
Income tax benefit	(1.7)				0.1			(1.6)	0.2
Equity in income of subsidiaries	0.0				0.0			0.0	0.0
Net income (loss)	7.0				(0.3)			6.6	(0.6)
Dividends on redeemable convertible preferred shares	0.0				0.0			0.0	0.0
Net income (loss) attributable to common shareholders	7.0				(0.3)			6.6	(0.6)
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	1,074.4				1,070.6			3,649.5	3,723.4
Cost of sales	(746.5)				(758.0)			(2,432.2)	(2,561.6)
Restructuring charges - cost of sales	(0.9)							(2.6)
Gross margin	327.0				312.6			1,214.7	1,104.3
Selling, general and administrative expenses	(387.3)				(378.3)			(1,257.0)	(1,230.4)
Credit transaction, net					(0.4)				(167.4)
Restructuring charges	(8.4)				(9.2)			(57.0)	(34.3)
Goodwill and intangible impairments								(35.2)	(448.7)
Other operating income, net	(0.1)				0.3			1.8	21.8
Operating income (loss)	(68.8)				(75.0)			(132.7)	(754.7)
Intra-entity interest income (expense)	(44.7)				(44.9)			(140.9)	(198.8)
Interest expense, net	(5.4)				(5.6)			(14.9)	(14.2)
Other non-operating income	(1.8)				0.3			(1.3)	1.4
Income (loss) before income taxes	(120.7)				(125.2)			(289.8)	(966.3)
Income tax benefit	15.4				53.1			38.2	157.6
Equity in income of subsidiaries	(90.4)				(92.8)			(272.8)	(865.7)
Net income (loss)	(195.7)				(164.9)			(524.4)	(1,674.4)
Dividends on redeemable convertible preferred shares	0.0				0.0			0.0	0.0
Net income (loss) attributable to common shareholders	(195.7)				(164.9)			(524.4)	(1,674.4)
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	113.3				121.1			334.3	369.0
Cost of sales	(72.1)				(62.5)			(220.0)	(184.6)
Restructuring charges - cost of sales	(0.5)							(3.2)
Gross margin	40.7				58.6			111.1	178.7
Selling, general and administrative expenses	(10.9)				(31.8)			(27.6)	(106.8)
Credit transaction, net					0.0				0.0
Restructuring charges	(0.8)				(0.3)			(2.4)	(1.3)
Goodwill and intangible impairments								(12.5)	0.0
Other operating income, net	0.1				(0.1)			(0.4)	3.8
Operating income (loss)	29.1				26.4			68.2	74.4
Intra-entity interest income (expense)	41.4				41.2			129.4	188.1
Interest expense, net	0.6				0.1			0.7	0.2
Other non-operating income	0.0				0.0			0.0	0.0
Income (loss) before income taxes	71.1				67.7			198.3	262.7
Income tax benefit	(7.7)				(24.0)			(32.9)	1.3
Equity in income of subsidiaries	(90.9)				(68.4)			(227.1)	(857.3)
Net income (loss)	(27.5)				(24.7)			(61.7)	(593.3)
Dividends on redeemable convertible preferred shares	0.0				0.0			0.0	0.0
Net income (loss) attributable to common shareholders	$ (27.5)				$ (24.7)			$ (61.7)	(593.3)
Restructuring Charges
Condensed Income Statements, Captions [Line Items]
Cost of sales									(63.2)
Restructuring Charges | Consolidation, Eliminations
Condensed Income Statements, Captions [Line Items]
Cost of sales									0.0
Restructuring Charges | Signet Jewelers Limited | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Cost of sales									0.0
Restructuring Charges | Signet UK Finance plc | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Cost of sales									0.0
Restructuring Charges | Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Cost of sales									(57.5)
Restructuring Charges | Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Cost of sales									$ (5.7)