Condensed consolidating financial information - Condensed consolidated income statement (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 28, 2017	Oct. 29, 2016	Oct. 28, 2017	Oct. 29, 2016
Condensed Income Statements, Captions [Line Items]
Sales	$ 1,156.9	$ 1,186.2	$ 3,959.9	$ 4,138.5
Cost of sales	(835.8)	(836.2)	(2,689.7)	(2,723.2)
Gross margin	321.1	350.0	1,270.2	1,415.3
Selling, general and administrative expenses	(375.9)	(386.5)	(1,237.7)	(1,264.9)
Credit transaction, net	(12.2)	0.0	2.6	0.0
Other operating income, net	72.5	68.6	221.3	213.6
Operating income	5.5	32.1	256.4	364.0
Intra-entity interest income (expense)	0.0	0.0	0.0	0.0
Interest expense, net	(16.6)	(12.7)	(42.7)	(36.4)
(Loss) income before income taxes	(11.1)	19.4	213.7	327.6
Income taxes	7.2	(2.4)	(45.7)	(81.9)
Equity in income of subsidiaries	0.0	0.0	0.0	0.0
Net (loss) income	(3.9)	17.0	168.0	245.7
Dividends on redeemable convertible preferred shares	(8.2)	(2.2)	(24.6)	(2.2)
Net income attributable to common shareholders	(12.1)	14.8	143.4	243.5
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
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
Other operating income, net	0.0	0.0	0.0	0.0
Operating income	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
(Loss) income before income taxes	0.0	0.0	0.0	0.0
Income taxes	0.0	0.0	0.0	0.0
Equity in income of subsidiaries	120.3	58.2	(138.8)	(388.5)
Net (loss) income	120.3	58.2	(138.8)	(388.5)
Dividends on redeemable convertible preferred shares	0.0	0.0	0.0	0.0
Net income attributable to common shareholders	120.3	58.2	(138.8)	(388.5)
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	1,067.0	1,121.8	3,714.5	3,955.0
Cost of sales	(799.9)	(821.7)	(2,623.1)	(2,688.0)
Gross margin	267.1	300.1	1,091.4	1,267.0
Selling, general and administrative expenses	(346.4)	(362.0)	(1,144.9)	(1,190.9)
Credit transaction, net	(12.2)		2.6
Other operating income, net	72.7	75.6	221.6	227.6
Operating income	(18.8)	13.7	170.7	303.7
Intra-entity interest income (expense)	(47.0)	(47.8)	(138.8)	(142.2)
Interest expense, net	(7.7)	(4.5)	(16.5)	(12.1)
(Loss) income before income taxes	(73.5)	(38.6)	15.4	149.4
Income taxes	28.3	15.1	(8.4)	(61.5)
Equity in income of subsidiaries	(71.5)	(51.9)	(41.2)	48.8
Net (loss) income	(116.7)	(75.4)	(34.2)	136.7
Dividends on redeemable convertible preferred shares	0.0	0.0	0.0	0.0
Net income attributable to common shareholders	(116.7)	(75.4)	(34.2)	136.7
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	89.9	64.4	245.4	183.5
Cost of sales	(35.9)	(14.5)	(66.6)	(35.2)
Gross margin	54.0	49.9	178.8	148.3
Selling, general and administrative expenses	(28.9)	(24.2)	(91.8)	(73.1)
Credit transaction, net	0.0		0.0
Other operating income, net	(0.2)	(7.0)	(0.3)	(14.0)
Operating income	24.9	18.7	86.7	61.2
Intra-entity interest income (expense)	42.3	43.1	124.7	128.1
Interest expense, net	(3.8)	(3.2)	(11.2)	(9.5)
(Loss) income before income taxes	63.4	58.6	200.2	179.8
Income taxes	(21.2)	(17.5)	(37.5)	(20.5)
Equity in income of subsidiaries	(45.5)	(23.6)	11.0	93.1
Net (loss) income	(3.3)	17.5	173.7	252.4
Dividends on redeemable convertible preferred shares	0.0	0.0	0.0	0.0
Net income attributable to common shareholders	(3.3)	17.5	173.7	252.4
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
Gross margin	0.0	0.0	0.0	0.0
Selling, general and administrative expenses	(0.6)	(0.3)	(1.0)	(0.9)
Credit transaction, net	0.0		0.0
Other operating income, net	0.0	0.0	0.0	0.0
Operating income	(0.6)	(0.3)	(1.0)	(0.9)
Intra-entity interest income (expense)	0.0	0.0	0.0	0.0
Interest expense, net	0.0	0.0	0.0	0.0
(Loss) income before income taxes	(0.6)	(0.3)	(1.0)	(0.9)
Income taxes	0.0	0.0	0.0	0.0
Equity in income of subsidiaries	(3.3)	17.3	169.0	246.6
Net (loss) income	(3.9)	17.0	168.0	245.7
Dividends on redeemable convertible preferred shares	8.2	(2.2)	(24.6)	(2.2)
Net income attributable to common shareholders	(12.1)	14.8	143.4	243.5
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
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
Other operating income, net	0.0	0.0	0.0	0.0
Operating income	0.0	0.0	0.0	0.0
Intra-entity interest income (expense)	4.7	4.7	14.1	14.1
Interest expense, net	(5.1)	(5.0)	(15.0)	(14.8)
(Loss) income before income taxes	(0.4)	(0.3)	(0.9)	(0.7)
Income taxes	0.1	0.0	0.2	0.1
Equity in income of subsidiaries	0.0	0.0	0.0	0.0
Net (loss) income	(0.3)	(0.3)	(0.7)	(0.6)
Dividends on redeemable convertible preferred shares	0.0	0.0	0.0	0.0
Net income attributable to common shareholders	$ (0.3)	$ (0.3)	$ (0.7)	$ (0.6)