Condensed consolidating financial information - Condensed consolidated income statement (Details) - USD ($) $ in Millions	3 Months Ended
	May 05, 2018	Apr. 29, 2017
Condensed Income Statements, Captions [Line Items]
Sales	$ 1,480.6	$ 1,403.4
Cost of sales	(995.8)	(912.2)
Gross margin	484.8	491.2
Selling, general and administrative expenses	(482.8)	(452.8)
Credit transaction, net	(143.1)	0.0
Restructuring charges	(6.5)	0.0
Goodwill and intangible impairments	(448.7)	0.0
Other operating income, net	22.1	76.9
Operating (loss) income	(574.2)	115.3
Intra-entity interest income (expense)	0.0	0.0
Interest expense, net	(8.9)	(12.6)
Other non-operating income	0.6	0.0
(Loss) income before income taxes	(582.5)	102.7
Income taxes	85.9	(24.2)
Equity in income of subsidiaries	0.0	0.0
Net (loss) income	(496.6)	78.5
Dividends on redeemable convertible preferred shares	(8.2)	(8.2)
Net income attributable to common shareholders	(504.8)	70.3
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
Goodwill and intangible impairments	0.0
Other operating income, net	0.0	0.0
Operating (loss) income	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
(Loss) income before income taxes	0.0	0.0
Income taxes	0.0	0.0
Equity in income of subsidiaries	1,628.7	(109.7)
Net (loss) income	1,628.7	(109.7)
Dividends on redeemable convertible preferred shares	0.0	0.0
Net income attributable to common shareholders	1,628.7	(109.7)
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	1,356.5	1,325.2
Cost of sales	(936.3)	(895.4)
Gross margin	420.2	429.8
Selling, general and administrative expenses	(444.4)	(421.5)
Credit transaction, net	(143.1)
Restructuring charges	(5.5)
Goodwill and intangible impairments	(448.7)
Other operating income, net	22.6	77.2
Operating (loss) income	(598.9)	85.5
Intra-entity interest income (expense)	(44.8)	(45.4)
Interest expense, net	(4.0)	(4.1)
Other non-operating income	0.6
(Loss) income before income taxes	(647.1)	36.0
Income taxes	79.4	(15.4)
Equity in income of subsidiaries	(565.1)	8.7
Net (loss) income	(1,132.8)	29.3
Dividends on redeemable convertible preferred shares	0.0	0.0
Net income attributable to common shareholders	(1,132.8)	29.3
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales	124.1	78.2
Cost of sales	(59.5)	(16.8)
Gross margin	64.6	61.4
Selling, general and administrative expenses	(38.3)	(31.1)
Credit transaction, net	0.0
Restructuring charges	(1.0)
Goodwill and intangible impairments	0.0
Other operating income, net	(0.4)	(0.3)
Operating (loss) income	24.9	30.0
Intra-entity interest income (expense)	40.8	40.7
Interest expense, net	0.0	(3.6)
Other non-operating income	0.0
(Loss) income before income taxes	65.7	67.1
Income taxes	6.5	(8.8)
Equity in income of subsidiaries	(567.9)	22.3
Net (loss) income	(495.7)	80.6
Dividends on redeemable convertible preferred shares	0.0	0.0
Net income attributable to common shareholders	(495.7)	80.6
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	(0.1)	(0.2)
Credit transaction, net	0.0
Restructuring charges	0.0
Goodwill and intangible impairments	0.0
Other operating income, net	(0.1)	0.0
Operating (loss) income	(0.2)	(0.2)
Intra-entity interest income (expense)	(0.7)	0.0
Interest expense, net	0.0	0.0
Other non-operating income	0.0
(Loss) income before income taxes	(0.9)	(0.2)
Income taxes	0.0	0.0
Equity in income of subsidiaries	(495.7)	78.7
Net (loss) income	(496.6)	78.5
Dividends on redeemable convertible preferred shares	(8.2)	(8.2)
Net income attributable to common shareholders	(504.8)	70.3
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
Goodwill and intangible impairments	0.0
Other operating income, net	0.0	0.0
Operating (loss) income	0.0	0.0
Intra-entity interest income (expense)	4.7	4.7
Interest expense, net	(4.9)	(4.9)
Other non-operating income	0.0
(Loss) income before income taxes	(0.2)	(0.2)
Income taxes	0.0	0.0
Equity in income of subsidiaries	0.0	0.0
Net (loss) income	(0.2)	(0.2)
Dividends on redeemable convertible preferred shares	0.0	0.0
Net income attributable to common shareholders	$ (0.2)	$ (0.2)