Condensed consolidating financial information - Condensed consolidated income statement (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 29, 2017	Jul. 30, 2016	Jul. 29, 2017	Jul. 30, 2016
Condensed Income Statements, Captions [Line Items]
Sales	$ 1,399.6	$ 1,373.4	$ 2,803.0	$ 2,952.3
Cost of sales	(941.7)	(908.5)	(1,853.9)	(1,887.0)
Gross margin	457.9	464.9	949.1	1,065.3
Selling, general and administrative expenses	(409.0)	(415.7)	(861.8)	(878.4)
Credit transaction, net	14.8	0.0	14.8	0.0
Other operating income, net	71.9	70.7	148.8	145.0
Operating income	135.6	119.9	250.9	331.9
Intra-entity interest income (expense)	0.0	0.0	0.0	0.0
Interest expense, net	(13.5)	(11.9)	(26.1)	(23.7)
Income before income taxes	122.1	108.0	224.8	308.2
Income taxes	(28.7)	(26.1)	(52.9)	(79.5)
Equity in income of subsidiaries	0.0	0.0	0.0	0.0
Net income	93.4	81.9	171.9	228.7
Dividends on redeemable convertible preferred shares	(8.2)	0.0	(16.4)	0.0
Net income attributable to common shareholders	85.2	81.9	155.5	228.7
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
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	(149.4)	(130.3)	(259.1)	(446.7)
Net income	(149.4)	(130.3)	(259.1)	(446.7)
Dividends on redeemable convertible preferred shares	0.0		0.0	0.0
Net income attributable to common shareholders	(149.4)	(130.3)	(259.1)	(446.7)
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	(0.2)	(0.5)	(0.4)	(0.6)
Credit transaction, net	0.0		0.0
Other operating income, net	0.0	0.0	0.0	0.0
Operating income	(0.2)	(0.5)	(0.4)	(0.6)
Intra-entity interest income (expense)	0.0	0.0	0.0	0.0
Interest expense, net	0.0	0.0	0.0	0.0
Income before income taxes	(0.2)	(0.5)	(0.4)	(0.6)
Income taxes	0.0	0.0	0.0	0.0
Equity in income of subsidiaries	93.6	82.4	172.3	229.3
Net income	93.4	81.9	171.9	228.7
Dividends on redeemable convertible preferred shares	(8.2)		(16.4)	0.0
Net income attributable to common shareholders	85.2	81.9	155.5	228.7
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	9.4	9.4
Interest expense, net	(5.0)	(4.9)	(9.9)	(9.8)
Income before income taxes	(0.3)	(0.2)	(0.5)	(0.4)
Income taxes	0.1	0.1	0.1	0.1
Equity in income of subsidiaries	0.0	0.0	0.0	0.0
Net income	(0.2)	(0.1)	(0.4)	(0.3)
Dividends on redeemable convertible preferred shares	0.0		0.0	0.0
Net income attributable to common shareholders	(0.2)	(0.1)	(0.4)	(0.3)
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	1,322.3	1,314.9	2,647.5	2,833.2
Cost of sales	(927.8)	(897.2)	(1,823.2)	(1,866.3)
Gross margin	394.5	417.7	824.3	966.9
Selling, general and administrative expenses	(377.0)	(390.3)	(798.5)	(828.9)
Credit transaction, net	14.8		14.8
Other operating income, net	71.7	80.4	148.9	152.0
Operating income	104.0	107.8	189.5	290.0
Intra-entity interest income (expense)	(46.4)	(47.5)	(91.8)	(94.4)
Interest expense, net	(4.7)	(3.9)	(8.8)	(7.6)
Income before income taxes	52.9	56.4	88.9	188.0
Income taxes	(21.3)	(22.4)	(36.7)	(76.6)
Equity in income of subsidiaries	21.6	15.5	30.3	100.7
Net income	53.2	49.5	82.5	212.1
Dividends on redeemable convertible preferred shares	0.0		0.0	0.0
Net income attributable to common shareholders	53.2	49.5	82.5	212.1
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	77.3	58.5	155.5	119.1
Cost of sales	(13.9)	(11.3)	(30.7)	(20.7)
Gross margin	63.4	47.2	124.8	98.4
Selling, general and administrative expenses	(31.8)	(24.9)	(62.9)	(48.9)
Credit transaction, net	0.0		0.0
Other operating income, net	0.2	(9.7)	(0.1)	(7.0)
Operating income	31.8	12.6	61.8	42.5
Intra-entity interest income (expense)	41.7	42.8	82.4	85.0
Interest expense, net	(3.8)	(3.1)	(7.4)	(6.3)
Income before income taxes	69.7	52.3	136.8	121.2
Income taxes	(7.5)	(3.8)	(16.3)	(3.0)
Equity in income of subsidiaries	34.2	32.4	56.5	116.7
Net income	96.4	80.9	177.0	234.9
Dividends on redeemable convertible preferred shares	0.0		0.0	0.0
Net income attributable to common shareholders	$ 96.4	$ 80.9	$ 177.0	$ 234.9