Condensed consolidating financial information - Condensed consolidated statement of operations (Details) - USD ($) $ in Millions	3 Months Ended
	May 04, 2019	May 05, 2018
Condensed Income Statements, Captions [Line Items]
Sales	$ 1,431.7	$ 1,480.6
Cost of sales	(932.3)	(995.8)
Gross margin	499.4	484.8
Selling, general and administrative expenses	(475.2)	(482.8)
Credit transaction, net	0.0	(143.1)
Restructuring charges	(26.8)	(6.5)
Goodwill and intangible impairments	0.0	(448.7)
Other operating income, net	0.0	22.1
Operating income (loss)	(2.6)	(574.2)
Intra-entity interest income (expense)	0.0	0.0
Interest expense, net	(9.2)	(8.9)
Other non-operating income	0.3	0.6
Income (loss) before income taxes	(11.5)	(582.5)
Income taxes	1.5	85.9
Equity in income of subsidiaries	0.0	0.0
Net income (loss)	(10.0)	(496.6)
Dividends on redeemable convertible preferred shares	(8.2)	(8.2)
Net income attributable to common shareholders	(18.2)	(504.8)
Consolidation, Eliminations
Condensed Income Statements, Captions [Line Items]
Sales	0.0	0.0
Cost of sales	0.0	0.0
Gross margin	0.0	0.0
Selling, general and administrative expenses	0.0	0.0
Credit transaction, net		0.0
Restructuring charges	0.0	0.0
Goodwill and intangible impairments		0.0
Other operating income, net	0.0	0.0
Operating income (loss)	0.0	0.0
Intra-entity interest income (expense)	0.0	0.0
Interest expense, net	0.0	0.0
Other non-operating income	0.0	0.0
Income (loss) before income taxes	0.0	0.0
Income taxes	0.0	0.0
Equity in income of subsidiaries	154.4	1,628.7
Net income (loss)	154.4	1,628.7
Dividends on redeemable convertible preferred shares	0.0	0.0
Net income attributable to common shareholders	154.4	1,628.7
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	1,316.9	1,356.5
Cost of sales	(854.0)	(936.3)
Gross margin	462.9	420.2
Selling, general and administrative expenses	(462.4)	(444.4)
Credit transaction, net		(143.1)
Restructuring charges	(25.8)	(5.5)
Goodwill and intangible impairments		(448.7)
Other operating income, net	(0.1)	22.6
Operating income (loss)	(25.4)	(598.9)
Intra-entity interest income (expense)	(48.4)	(44.8)
Interest expense, net	(4.3)	(4.0)
Other non-operating income	0.3	0.6
Income (loss) before income taxes	(77.8)	(647.1)
Income taxes	8.8	79.4
Equity in income of subsidiaries	(79.7)	(565.1)
Net income (loss)	(148.7)	(1,132.8)
Dividends on redeemable convertible preferred shares	0.0	0.0
Net income attributable to common shareholders	(148.7)	(1,132.8)
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	114.8	124.1
Cost of sales	(78.3)	(59.5)
Gross margin	36.5	64.6
Selling, general and administrative expenses	(12.8)	(38.3)
Credit transaction, net		0.0
Restructuring charges	(1.0)	(1.0)
Goodwill and intangible impairments		0.0
Other operating income, net	0.1	(0.4)
Operating income (loss)	22.8	24.9
Intra-entity interest income (expense)	44.4	40.8
Interest expense, net	0.1	0.0
Other non-operating income	0.0	0.0
Income (loss) before income taxes	67.3	65.7
Income taxes	(7.4)	6.5
Equity in income of subsidiaries	(65.4)	(567.9)
Net income (loss)	(5.5)	(495.7)
Dividends on redeemable convertible preferred shares	0.0	0.0
Net income attributable to common shareholders	(5.5)	(495.7)
Signet Jewelers Limited | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	0.0	0.0
Cost of sales	0.0	0.0
Gross margin	0.0	0.0
Selling, general and administrative expenses	0.0	(0.1)
Credit transaction, net		0.0
Restructuring charges	0.0	0.0
Goodwill and intangible impairments		0.0
Other operating income, net	0.0	(0.1)
Operating income (loss)	0.0	(0.2)
Intra-entity interest income (expense)	(0.7)	(0.7)
Interest expense, net	0.0	0.0
Other non-operating income	0.0	0.0
Income (loss) before income taxes	(0.7)	(0.9)
Income taxes	0.0	0.0
Equity in income of subsidiaries	(9.3)	(495.7)
Net income (loss)	(10.0)	(496.6)
Dividends on redeemable convertible preferred shares	(8.2)	(8.2)
Net income attributable to common shareholders	(18.2)	(504.8)
Signet UK Finance plc | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	0.0	0.0
Cost of sales	0.0	0.0
Gross margin	0.0	0.0
Selling, general and administrative expenses	0.0	0.0
Credit transaction, net		0.0
Restructuring charges	0.0	0.0
Goodwill and intangible impairments		0.0
Other operating income, net	0.0	0.0
Operating income (loss)	0.0	0.0
Intra-entity interest income (expense)	4.7	4.7
Interest expense, net	(5.0)	(4.9)
Other non-operating income	0.0	0.0
Income (loss) before income taxes	(0.3)	(0.2)
Income taxes	0.1	0.0
Equity in income of subsidiaries	0.0	0.0
Net income (loss)	(0.2)	(0.2)
Dividends on redeemable convertible preferred shares	0.0	0.0
Net income attributable to common shareholders	$ (0.2)	$ (0.2)