Condensed consolidating financial information - Condensed consolidated statement of comprehensive income (loss) (Details) - USD ($) $ in Millions		3 Months Ended
		May 05, 2018	Apr. 29, 2017
Condensed Statement of Comprehensive Income [Line Items]
Net income		$ (496.6)	$ 78.5
Other comprehensive income (loss):
Foreign currency translation adjustments		(21.7)	0.5
Available-for-sale securities:
Unrealized loss	[1]	(0.2)	0.2
Impact from adoption of new accounting pronouncements	[2]	(0.8)
Cash flow hedges:
Unrealized gain		1.5	2.7
Reclassification adjustment for losses to net income		(0.3)	(1.4)
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss		0.3	0.6
Reclassification adjustment to net income for amortization of prior service credits		(0.1)	(0.3)
Total other comprehensive loss		(21.3)	2.3
Total comprehensive loss		(517.9)	80.8
Consolidation, Eliminations
Condensed Statement of Comprehensive Income [Line Items]
Net income		1,628.7	(109.7)
Other comprehensive income (loss):
Foreign currency translation adjustments		21.7	(0.5)
Available-for-sale securities:
Unrealized loss		0.2	(0.2)
Impact from adoption of new accounting pronouncements		0.8
Cash flow hedges:
Unrealized gain		(1.5)	(2.7)
Reclassification adjustment for losses to net income		0.3	1.4
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss		(0.3)	(0.6)
Reclassification adjustment to net income for amortization of prior service credits		0.1	0.3
Total other comprehensive loss		21.3	(2.3)
Total comprehensive loss		1,650.0	(112.0)
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income		(1,132.8)	29.3
Other comprehensive income (loss):
Foreign currency translation adjustments		(21.5)	0.5
Available-for-sale securities:
Unrealized loss		0.0	0.0
Impact from adoption of new accounting pronouncements		0.0
Cash flow hedges:
Unrealized gain		1.5	2.7
Reclassification adjustment for losses to net income		(0.3)	(1.4)
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss		0.3	0.6
Reclassification adjustment to net income for amortization of prior service credits		(0.1)	(0.3)
Total other comprehensive loss		(20.1)	2.1
Total comprehensive loss		(1,152.9)	31.4
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income		(495.7)	80.6
Other comprehensive income (loss):
Foreign currency translation adjustments		(0.2)
Available-for-sale securities:
Unrealized loss		(0.2)	0.2
Impact from adoption of new accounting pronouncements		(0.8)
Cash flow hedges:
Unrealized 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		0.0	0.0
Total other comprehensive loss		(1.2)	0.2
Total comprehensive loss		(496.9)	80.8
Signet Jewelers Limited | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income		(496.6)	78.5
Other comprehensive income (loss):
Foreign currency translation adjustments		(21.7)	0.5
Available-for-sale securities:
Unrealized loss		(0.2)	0.2
Impact from adoption of new accounting pronouncements		(0.8)
Cash flow hedges:
Unrealized gain		1.5	2.7
Reclassification adjustment for losses to net income		(0.3)	(1.4)
Pension plan:
Reclassification adjustment to net income for amortization of actuarial loss		0.3	0.6
Reclassification adjustment to net income for amortization of prior service credits		(0.1)	(0.3)
Total other comprehensive loss		(21.3)	2.3
Total comprehensive loss		(517.9)	80.8
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
Impact from adoption of new accounting pronouncements		0.0
Cash flow hedges:
Unrealized 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		0.0	0.0
Total other comprehensive loss		0.0	0.0
Total comprehensive loss		$ (0.2)	$ (0.2)

[1] During the 13 weeks ended May 5, 2018, amount represents unrealized losses related to the Company’s available-for-sale debt securities. During the 13 weeks ended April 29, 2017, amount represents unrealized gains related to the Company’s available-for-sale debt and equity securities.

[2] Adjustment reflects the reclassification of unrealized gains related to the Company’s equity security investments as of February 3, 2018 from AOCI into retained earnings associated with the adoption of ASU 2016-1.