Condensed consolidating financial information - Condensed consolidated income statement (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Nov. 03, 2018	Oct. 28, 2017	Nov. 03, 2018	Oct. 28, 2017
Condensed Income Statements, Captions [Line Items]
Sales	$ 1,191.7	$ 1,156.9	$ 4,092.4	$ 3,959.9
Cost of sales	(820.5)	(835.8)	(2,746.2)	(2,689.7)
Gross margin	371.2	321.1	1,283.0	1,270.2
Selling, general and administrative expenses	(410.3)	(375.9)	(1,337.9)	(1,237.7)
Credit transaction, net	(0.4)	(12.2)	(167.4)	2.6
Restructuring charges	(9.5)	0.0	(35.6)	0.0
Goodwill and intangible impairments	0.0	0.0	(448.7)	0.0
Other operating income, net	0.2	72.5	25.5	221.3
Operating income (loss)	(48.8)	5.5	(681.1)	256.4
Intra-entity interest income (expense)	0.0	0.0	0.0	0.0
Interest expense, net	(10.6)	(16.6)	(28.9)	(42.7)
Other non-operating income	0.3	0.0	1.4	0.0
Income (loss) before income taxes	(59.1)	(11.1)	(708.6)	213.7
Income taxes	29.2	7.2	159.1	(45.7)
Equity in income of subsidiaries	0.0	0.0	0.0	0.0
Net income (loss)	(29.9)	(3.9)	(549.5)	168.0
Dividends on redeemable convertible preferred shares	(8.2)	(8.2)	(24.6)	(24.6)
Net income attributable to common shareholders	(38.1)	(12.1)	(574.1)	143.4
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	0.0	0.0
Restructuring charges	0.0		0.0
Goodwill and intangible impairments			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
Income (loss) 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	189.9	120.3	2,268.3	(138.8)
Net income (loss)	189.9	120.3	2,268.3	(138.8)
Dividends on redeemable convertible preferred shares	0.0	0.0	0.0	0.0
Net income attributable to common shareholders	189.9	120.3	2,268.3	(138.8)
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	1,070.6	1,067.0	3,723.4	3,714.5
Cost of sales	(758.0)	(799.9)	(2,561.6)	(2,623.1)
Gross margin	312.6	267.1	1,104.3	1,091.4
Selling, general and administrative expenses	(378.3)	(346.4)	(1,230.4)	(1,144.9)
Credit transaction, net	(0.4)	(12.2)	(167.4)	2.6
Restructuring charges	(9.2)		(34.3)
Goodwill and intangible impairments			(448.7)
Other operating income, net	0.3	72.7	21.8	221.6
Operating income (loss)	(75.0)	(18.8)	(754.7)	170.7
Intra-entity interest income (expense)	(44.9)	(47.0)	(198.8)	(138.8)
Interest expense, net	(5.6)	(7.7)	(14.2)	(16.5)
Other non-operating income	0.3		1.4
Income (loss) before income taxes	(125.2)	(73.5)	(966.3)	15.4
Income taxes	53.1	28.3	157.6	(8.4)
Equity in income of subsidiaries	(92.8)	(71.5)	(865.7)	(41.2)
Net income (loss)	(164.9)	(116.7)	(1,674.4)	(34.2)
Dividends on redeemable convertible preferred shares	0.0	0.0	0.0	0.0
Net income attributable to common shareholders	(164.9)	(116.7)	(1,674.4)	(34.2)
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	121.1	89.9	369.0	245.4
Cost of sales	(62.5)	(35.9)	(184.6)	(66.6)
Gross margin	58.6	54.0	178.7	178.8
Selling, general and administrative expenses	(31.8)	(28.9)	(106.8)	(91.8)
Credit transaction, net	0.0	0.0	0.0	0.0
Restructuring charges	(0.3)		(1.3)
Goodwill and intangible impairments			0.0
Other operating income, net	(0.1)	(0.2)	3.8	(0.3)
Operating income (loss)	26.4	24.9	74.4	86.7
Intra-entity interest income (expense)	41.2	42.3	188.1	124.7
Interest expense, net	0.1	(3.8)	0.2	(11.2)
Other non-operating income	0.0		0.0
Income (loss) before income taxes	67.7	63.4	262.7	200.2
Income taxes	(24.0)	(21.2)	1.3	(37.5)
Equity in income of subsidiaries	(68.4)	(45.5)	(857.3)	11.0
Net income (loss)	(24.7)	(3.3)	(593.3)	173.7
Dividends on redeemable convertible preferred shares	0.0	0.0	0.0	0.0
Net income attributable to common shareholders	(24.7)	(3.3)	(593.3)	173.7
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)	(0.6)	(0.7)	(1.0)
Credit transaction, net	0.0	0.0	0.0	0.0
Restructuring charges	0.0		0.0
Goodwill and intangible impairments			0.0
Other operating income, net	0.0	0.0	(0.1)	0.0
Operating income (loss)	(0.2)	(0.6)	(0.8)	(1.0)
Intra-entity interest income (expense)	(1.0)	0.0	(3.4)	0.0
Interest expense, net	0.0	0.0	0.0	0.0
Other non-operating income	0.0		0.0
Income (loss) before income taxes	(1.2)	(0.6)	(4.2)	(1.0)
Income taxes	0.0	0.0	0.0	0.0
Equity in income of subsidiaries	(28.7)	(3.3)	(545.3)	169.0
Net income (loss)	(29.9)	(3.9)	(549.5)	168.0
Dividends on redeemable convertible preferred shares	(8.2)	(8.2)	(24.6)	(24.6)
Net income attributable to common shareholders	(38.1)	(12.1)	(574.1)	143.4
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	0.0	0.0
Restructuring charges	0.0		0.0
Goodwill and intangible impairments			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)	4.7	4.7	14.1	14.1
Interest expense, net	(5.1)	(5.1)	(14.9)	(15.0)
Other non-operating income	0.0		0.0
Income (loss) before income taxes	(0.4)	(0.4)	(0.8)	(0.9)
Income taxes	0.1	0.1	0.2	0.2
Equity in income of subsidiaries	0.0	0.0	0.0	0.0
Net income (loss)	(0.3)	(0.3)	(0.6)	(0.7)
Dividends on redeemable convertible preferred shares	0.0	0.0	0.0	0.0
Net income attributable to common shareholders	(0.3)	(0.3)	(0.6)	(0.7)
Restructuring Charges
Condensed Income Statements, Captions [Line Items]
Cost of sales	$ 0.0	$ 0.0	(63.2)	$ 0.0
Restructuring Charges | Consolidation, Eliminations
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)
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