Condensed consolidating financial information - Condensed consolidated statement of comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 29, 2017	Jul. 30, 2016	Jul. 29, 2017	Jul. 30, 2016
Condensed Statement of Comprehensive Income [Line Items]
Net income	$ 93.4	$ 81.9	$ 171.9	$ 228.7
Other comprehensive income (loss):
Foreign currency translation adjustments	24.6	(39.9)	25.1	(9.1)
Available-for-sale securities:
Unrealized loss	0.3	0.2	0.5	0.4
Cash flow hedges:
Unrealized (loss) gain	(0.9)	2.7	1.8	6.3
Reclassification adjustment for losses to net income	(1.1)	0.6	(2.5)	1.7
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss	0.6	0.3	1.2	0.6
Reclassification adjustment to net income for amortization of prior service credits	(0.4)	(0.4)	(0.7)	(0.8)
Total other comprehensive income (loss)	23.1	(36.5)	25.4	(0.9)
Total comprehensive income	116.5	45.4	197.3	227.8
Consolidation, Eliminations
Condensed Statement of Comprehensive Income [Line Items]
Net income	(149.4)	(130.3)	(259.1)	(446.7)
Other comprehensive income (loss):
Foreign currency translation adjustments	(24.6)	39.9	(25.1)	9.1
Available-for-sale securities:
Unrealized loss	(0.3)	(0.2)	(0.5)	(0.4)
Cash flow hedges:
Unrealized (loss) gain	0.9	(2.7)	(1.8)	(6.3)
Reclassification adjustment for losses to net income	1.1	(0.6)	2.5	(1.7)
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss	(0.6)	(0.3)	(1.2)	(0.6)
Reclassification adjustment to net income for amortization of prior service credits	0.4	0.4	0.7	0.8
Total other comprehensive income (loss)	(23.1)	36.5	(25.4)	0.9
Total comprehensive income	(172.5)	(93.8)	(284.5)	(445.8)
Signet Jewelers Limited | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income	93.4	81.9	171.9	228.7
Other comprehensive income (loss):
Foreign currency translation adjustments	24.6	(39.9)	25.1	(9.1)
Available-for-sale securities:
Unrealized loss	0.3	0.2	0.5	0.4
Cash flow hedges:
Unrealized (loss) gain	(0.9)	2.7	1.8	6.3
Reclassification adjustment for losses to net income	(1.1)	0.6	(2.5)	1.7
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss	0.6	0.3	1.2	0.6
Reclassification adjustment to net income for amortization of prior service credits	(0.4)	(0.4)	(0.7)	(0.8)
Total other comprehensive income (loss)	23.1	(36.5)	25.4	(0.9)
Total comprehensive income	116.5	45.4	197.3	227.8
Signet UK Finance plc | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income	(0.2)	(0.1)	(0.4)	(0.3)
Other comprehensive income (loss):
Foreign currency translation adjustments	0.0	0.0	0.0	0.0
Available-for-sale securities:
Unrealized loss	0.0	0.0	0.0	0.0
Cash flow hedges:
Unrealized (loss) gain	0.0	0.0	0.0	0.0
Reclassification adjustment for losses to net income	0.0	0.0	0.0	0.0
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss	0.0	0.0	0.0	0.0
Reclassification adjustment to net income for amortization of prior service credits	0.0	0.0	0.0	0.0
Total other comprehensive income (loss)	0.0	0.0	0.0	0.0
Total comprehensive income	(0.2)	(0.1)	(0.4)	(0.3)
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income	53.2	49.5	82.5	212.1
Other comprehensive income (loss):
Foreign currency translation adjustments	24.6	(44.9)	25.1	(12.7)
Available-for-sale securities:
Unrealized loss	0.0	0.0	0.0	0.0
Cash flow hedges:
Unrealized (loss) gain	(0.9)	2.7	1.8	6.3
Reclassification adjustment for losses to net income	(1.1)	0.6	(2.5)	1.7
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss	0.6	0.3	1.2	0.6
Reclassification adjustment to net income for amortization of prior service credits	(0.4)	(0.4)	(0.7)	(0.8)
Total other comprehensive income (loss)	22.8	(41.7)	24.9	(4.9)
Total comprehensive income	76.0	7.8	107.4	207.2
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income	96.4	80.9	177.0	234.9
Other comprehensive income (loss):
Foreign currency translation adjustments		5.0		3.6
Available-for-sale securities:
Unrealized loss	0.3	0.2	0.5	0.4
Cash flow hedges:
Unrealized (loss) gain	0.0	0.0	0.0	0.0
Reclassification adjustment for losses to net income	0.0	0.0	0.0	0.0
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss	0.0	0.0	0.0	0.0
Reclassification adjustment to net income for amortization of prior service credits	0.0	0.0	0.0	0.0
Total other comprehensive income (loss)	0.3	5.2	0.5	4.0
Total comprehensive income	$ 96.7	$ 86.1	$ 177.5	$ 238.9