Condensed consolidating financial information - Condensed consolidated statement of comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 29, 2017	Apr. 30, 2016
Condensed Statement of Comprehensive Income [Line Items]
Net income	$ 78.5	$ 146.8
Other comprehensive income (loss):
Foreign currency translation adjustments	0.5	30.8
Available-for-sale securities:
Unrealized loss	0.2	0.2
Cash flow hedges:
Unrealized (loss) gain	2.7	3.6
Reclassification adjustment for losses to net income	(1.4)	1.1
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss	0.6	0.3
Reclassification adjustment to net income for amortization of prior service (credits) costs	(0.3)	(0.4)
Total other comprehensive income	2.3	35.6
Total comprehensive income	80.8	182.4
Consolidation, Eliminations
Condensed Statement of Comprehensive Income [Line Items]
Net income	(109.7)	(316.4)
Other comprehensive income (loss):
Foreign currency translation adjustments	(0.5)	(30.8)
Available-for-sale securities:
Unrealized loss	(0.2)	(0.2)
Cash flow hedges:
Unrealized (loss) gain	(2.7)	(3.6)
Reclassification adjustment for losses to net income	1.4	(1.1)
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss	(0.6)	(0.3)
Reclassification adjustment to net income for amortization of prior service (credits) costs	0.3	0.4
Total other comprehensive income	(2.3)	(35.6)
Total comprehensive income	(112.0)	(352.0)
Signet Jewelers Limited | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income	78.5	146.8
Other comprehensive income (loss):
Foreign currency translation adjustments	0.5	30.8
Available-for-sale securities:
Unrealized loss	0.2	0.2
Cash flow hedges:
Unrealized (loss) gain	2.7	3.6
Reclassification adjustment for losses to net income	(1.4)	1.1
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss	0.6	0.3
Reclassification adjustment to net income for amortization of prior service (credits) costs	(0.3)	(0.4)
Total other comprehensive income	2.3	35.6
Total comprehensive income	80.8	182.4
Signet UK Finance plc | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income	(0.2)	(0.2)
Other comprehensive income (loss):
Foreign currency translation adjustments	0.0	0.0
Available-for-sale securities:
Unrealized loss	0.0	0.0
Cash flow hedges:
Unrealized (loss) gain	0.0	0.0
Reclassification adjustment for losses to net income	0.0	0.0
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss	0.0	0.0
Reclassification adjustment to net income for amortization of prior service (credits) costs	0.0	0.0
Total other comprehensive income	0.0	0.0
Total comprehensive income	(0.2)	(0.2)
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income	29.3	162.6
Other comprehensive income (loss):
Foreign currency translation adjustments	0.5	32.2
Available-for-sale securities:
Unrealized loss	0.0	0.0
Cash flow hedges:
Unrealized (loss) gain	2.7	3.6
Reclassification adjustment for losses to net income	(1.4)	1.1
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss	0.6	0.3
Reclassification adjustment to net income for amortization of prior service (credits) costs	(0.3)	(0.4)
Total other comprehensive income	2.1	36.8
Total comprehensive income	31.4	199.4
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income	80.6	154.0
Other comprehensive income (loss):
Foreign currency translation adjustments		(1.4)
Available-for-sale securities:
Unrealized loss	0.2	0.2
Cash flow hedges:
Unrealized (loss) gain	0.0	0.0
Reclassification adjustment for losses to net income	0.0	0.0
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss	0.0	0.0
Reclassification adjustment to net income for amortization of prior service (credits) costs	0.0	0.0
Total other comprehensive income	0.2	(1.2)
Total comprehensive income	$ 80.8	$ 152.8