Condensed consolidating financial information - Condensed consolidated statement of comprehensive income (loss) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Nov. 03, 2018	Oct. 28, 2017	Nov. 03, 2018	Oct. 28, 2017
Condensed Statement of Comprehensive Income [Line Items]
Net income		$ (29.9)	$ (3.9)	$ (549.5)	$ 168.0
Other comprehensive income (loss):
Foreign currency translation adjustments		(2.5)	(6.5)	(39.5)	18.6
Available-for-sale securities:
Unrealized loss	[1]	0.0	(0.2)	0.3	0.3
Impact from adoption of new accounting pronouncements	[2]			(0.8)
Cash flow hedges:
Unrealized gain		2.3	0.9	0.8	2.7
Reclassification adjustment for losses to net income		(0.5)	(0.6)	(1.0)	(3.1)
Pension plan:
Actuarial loss		0.0	(0.9)	(6.5)	(0.9)
Reclassification adjustment to net income for amortization of actuarial loss		0.2	0.6	0.5	1.8
Reclassification adjustment to net income for amortization of prior service credits		0.0	(0.4)	0.0	(1.1)
Net curtailment gain and settlement loss		0.0	(3.0)	0.0	(3.0)
Total other comprehensive loss		(0.5)	(10.1)	(46.2)	15.3
Total comprehensive loss		(30.4)	(14.0)	(595.7)	183.3
Consolidation, Eliminations
Condensed Statement of Comprehensive Income [Line Items]
Net income		189.9	120.3	2,268.3	(138.8)
Other comprehensive income (loss):
Foreign currency translation adjustments		2.5	6.5	39.5	(18.6)
Available-for-sale securities:
Unrealized loss			0.2	(0.3)	(0.3)
Impact from adoption of new accounting pronouncements				0.8
Cash flow hedges:
Unrealized gain		(2.3)	(0.9)	(0.8)	(2.7)
Reclassification adjustment for losses to net income		0.5	0.6	1.0	3.1
Pension plan:
Actuarial loss			0.9	6.5	0.9
Reclassification adjustment to net income for amortization of actuarial loss		(0.2)	(0.6)	(0.5)	(1.8)
Reclassification adjustment to net income for amortization of prior service credits			0.4		1.1
Net curtailment gain and settlement loss			3.0		3.0
Total other comprehensive loss		0.5	10.1	46.2	(15.3)
Total comprehensive loss		190.4	130.4	2,314.5	(154.1)
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income		(164.9)	(116.7)	(1,674.4)	(34.2)
Other comprehensive income (loss):
Foreign currency translation adjustments		(2.5)	(6.5)	(39.0)	18.6
Available-for-sale securities:
Unrealized loss			0.0	0.0	0.0
Impact from adoption of new accounting pronouncements				0.0
Cash flow hedges:
Unrealized gain		2.3	0.9	0.8	2.7
Reclassification adjustment for losses to net income		(0.5)	(0.6)	(1.0)	(3.1)
Pension plan:
Actuarial loss			(0.9)	(6.5)	(0.9)
Reclassification adjustment to net income for amortization of actuarial loss		0.2	0.6	0.5	1.8
Reclassification adjustment to net income for amortization of prior service credits			(0.4)		(1.1)
Net curtailment gain and settlement loss			(3.0)		(3.0)
Total other comprehensive loss		(0.5)	(9.9)	(45.2)	15.0
Total comprehensive loss		(165.4)	(126.6)	(1,719.6)	(19.2)
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income		(24.7)	(3.3)	(593.3)	173.7
Other comprehensive income (loss):
Foreign currency translation adjustments				(0.5)
Available-for-sale securities:
Unrealized loss			(0.2)	0.3	0.3
Impact from adoption of new accounting pronouncements				(0.8)
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	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
Net curtailment gain and settlement loss			0.0		0.0
Total other comprehensive loss			(0.2)	(1.0)	0.3
Total comprehensive loss		(24.7)	(3.5)	(594.3)	174.0
Signet Jewelers Limited | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income		(29.9)	(3.9)	(549.5)	168.0
Other comprehensive income (loss):
Foreign currency translation adjustments		(2.5)	(6.5)	(39.5)	18.6
Available-for-sale securities:
Unrealized loss			(0.2)	0.3	0.3
Impact from adoption of new accounting pronouncements				(0.8)
Cash flow hedges:
Unrealized gain		2.3	0.9	0.8	2.7
Reclassification adjustment for losses to net income		(0.5)	(0.6)	(1.0)	(3.1)
Pension plan:
Actuarial loss			(0.9)	(6.5)	(0.9)
Reclassification adjustment to net income for amortization of actuarial loss		0.2	0.6	0.5	1.8
Reclassification adjustment to net income for amortization of prior service credits			(0.4)		(1.1)
Net curtailment gain and settlement loss			(3.0)		(3.0)
Total other comprehensive loss		(0.5)	(10.1)	(46.2)	15.3
Total comprehensive loss		(30.4)	(14.0)	(595.7)	183.3
Signet UK Finance plc | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income		(0.3)	(0.3)	(0.6)	(0.7)
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
Impact from adoption of new accounting pronouncements				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	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
Net curtailment gain and settlement loss			0.0
Total other comprehensive loss				0.0	0.0
Total comprehensive loss		$ (0.3)	$ (0.3)	$ (0.6)	$ (0.7)

[1] During the 13 and 39 weeks ended November 3, 2018, amounts represent unrealized gains (losses) related to the Company’s available-for-sale debt securities. During the 13 and 39 weeks ended October 28, 2017, amounts represent unrealized gains and losses 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 available-for-sale equity securities as of February 3, 2018 from AOCI into retained earnings associated with the adoption of ASU 2016-1.