Condensed consolidating financial information - Condensed consolidated statement of comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Oct. 28, 2017	Oct. 29, 2016	Oct. 28, 2017	Oct. 29, 2016
Condensed Statement of Comprehensive Income [Line Items]
Net income	$ (3.9)	$ 17.0	$ 168.0	$ 245.7
Other comprehensive income (loss):
Foreign currency translation adjustments	(6.5)	(28.9)	18.6	(38.0)
Available-for-sale securities:
Unrealized loss	(0.2)	(0.2)	0.3	0.2
Cash flow hedges:
Unrealized gain	0.9	1.9	2.7	8.2
Reclassification adjustment for losses to net income	(0.6)	(0.1)	(3.1)	1.6
Pension plan:
Actuarial loss	(0.9)	0.0	(0.9)	0.0
Reclassification adjustment to net income for amortization of actuarial loss	0.6	0.4	1.8	1.0
Reclassification adjustment to net income for amortization of prior service credits	(0.4)	(0.4)	(1.1)	(1.2)
Net curtailment gain and settlement loss	(3.0)	0.0	(3.0)	0.0
Total other comprehensive loss	(10.1)	(27.3)	15.3	(28.2)
Total comprehensive loss	(14.0)	(10.3)	183.3	217.5
Consolidation, Eliminations
Condensed Statement of Comprehensive Income [Line Items]
Net income	120.3	58.2	(138.8)	(388.5)
Other comprehensive income (loss):
Foreign currency translation adjustments	6.5	28.9	(18.6)	38.0
Available-for-sale securities:
Unrealized loss	0.2	0.2	(0.3)	(0.2)
Cash flow hedges:
Unrealized gain	(0.9)	(1.9)	(2.7)	(8.2)
Reclassification adjustment for losses to net income	0.6	0.1	3.1	(1.6)
Pension plan:
Actuarial loss	0.9		0.9
Reclassification adjustment to net income for amortization of actuarial loss	(0.6)	(0.4)	(1.8)	(1.0)
Reclassification adjustment to net income for amortization of prior service credits	0.4	0.4	1.1	1.2
Net curtailment gain and settlement loss	3.0		3.0
Total other comprehensive loss	10.1	27.3	(15.3)	28.2
Total comprehensive loss	130.4	85.5	(154.1)	(360.3)
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income	(116.7)	(75.4)	(34.2)	136.7
Other comprehensive income (loss):
Foreign currency translation adjustments	(6.5)	(32.5)	18.6	(45.2)
Available-for-sale securities:
Unrealized loss	0.0	0.0	0.0	0.0
Cash flow hedges:
Unrealized gain	0.9	1.9	2.7	8.2
Reclassification adjustment for losses to net income	(0.6)	(0.1)	(3.1)	1.6
Pension plan:
Actuarial loss	(0.9)		(0.9)
Reclassification adjustment to net income for amortization of actuarial loss	0.6	0.4	1.8	1.0
Reclassification adjustment to net income for amortization of prior service credits	(0.4)	(0.4)	(1.1)	(1.2)
Net curtailment gain and settlement loss	(3.0)		(3.0)
Total other comprehensive loss	(9.9)	(30.7)	15.0	(35.6)
Total comprehensive loss	(126.6)	(106.1)	(19.2)	101.1
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income	(3.3)	17.5	173.7	252.4
Other comprehensive income (loss):
Foreign currency translation adjustments		3.6		7.2
Available-for-sale securities:
Unrealized loss	(0.2)	(0.2)	0.3	0.2
Cash flow hedges:
Unrealized 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:
Actuarial loss	0.0		0.0
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
Net curtailment gain and settlement loss	0.0
Total other comprehensive loss	(0.2)	3.4	0.3	7.4
Total comprehensive loss	(3.5)	20.9	174.0	259.8
Signet Jewelers Limited | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income	(3.9)	17.0	168.0	245.7
Other comprehensive income (loss):
Foreign currency translation adjustments	(6.5)	(28.9)	18.6	(38.0)
Available-for-sale securities:
Unrealized loss	(0.2)	(0.2)	0.3	0.2
Cash flow hedges:
Unrealized gain	0.9	1.9	2.7	8.2
Reclassification adjustment for losses to net income	(0.6)	(0.1)	(3.1)	1.6
Pension plan:
Actuarial loss	(0.9)		(0.9)
Reclassification adjustment to net income for amortization of actuarial loss	0.6	0.4	1.8	1.0
Reclassification adjustment to net income for amortization of prior service credits	(0.4)	(0.4)	(1.1)	(1.2)
Net curtailment gain and settlement loss	(3.0)		(3.0)
Total other comprehensive loss	(10.1)	(27.3)	15.3	(28.2)
Total comprehensive loss	(14.0)	(10.3)	183.3	217.5
Signet UK Finance plc | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income	(0.3)	(0.3)	(0.7)	(0.6)
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 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:
Actuarial loss	0.0		0.0
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
Net curtailment gain and settlement loss	0.0		0.0
Total other comprehensive loss	0.0	0.0	0.0	0.0
Total comprehensive loss	$ (0.3)	$ (0.3)	$ (0.7)	$ (0.6)