Condensed consolidating financial information - Condensed consolidated statement of comprehensive income (loss) (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Aug. 04, 2018	Jul. 29, 2017	Aug. 04, 2018	Jul. 29, 2017
Condensed Statement of Comprehensive Income [Line Items]
Net income		$ (23.0)	$ 93.4	$ (519.6)	$ 171.9
Other comprehensive income (loss):
Foreign currency translation adjustments		(15.3)	24.6	(37.0)	25.1
Available-for-sale securities:
Unrealized loss	[1]	0.5	0.3	0.3	0.5
Impact from adoption of new accounting pronouncements	[2]			(0.8)
Cash flow hedges:
Unrealized gain		(3.0)	(0.9)	(1.5)	1.8
Reclassification adjustment for losses to net income		(0.2)	(1.1)	(0.5)	(2.5)
Pension plan:
Actuarial loss		(6.5)	0.0	(6.5)	0.0
Reclassification adjustment to net income for amortization of actuarial loss		0.0	0.6	0.3	1.2
Reclassification adjustment to net income for amortization of prior service credits		0.1	(0.4)	0.0	(0.7)
Total other comprehensive loss		(24.4)	23.1	(45.7)	25.4
Total comprehensive loss		(47.4)	116.5	(565.3)	197.3
Consolidation, Eliminations
Condensed Statement of Comprehensive Income [Line Items]
Net income		449.7	(149.4)	2,078.4	(259.1)
Other comprehensive income (loss):
Foreign currency translation adjustments		15.3	(24.6)	37.0	(25.1)
Available-for-sale securities:
Unrealized loss		(0.5)	(0.3)	(0.3)	(0.5)
Impact from adoption of new accounting pronouncements				0.8
Cash flow hedges:
Unrealized gain		3.0	0.9	1.5	(1.8)
Reclassification adjustment for losses to net income		0.2	1.1	0.5	2.5
Pension plan:
Actuarial loss		6.5		6.5
Reclassification adjustment to net income for amortization of actuarial loss			(0.6)	(0.3)	(1.2)
Reclassification adjustment to net income for amortization of prior service credits		(0.1)	0.4		0.7
Total other comprehensive loss		24.4	(23.1)	45.7	(25.4)
Total comprehensive loss		474.1	(172.5)	2,124.1	(284.5)
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income		(376.7)	53.2	(1,509.5)	82.5
Other comprehensive income (loss):
Foreign currency translation adjustments		(15.0)	24.6	(36.5)	25.1
Available-for-sale securities:
Unrealized loss		0.0	0.0	0.0	0.0
Impact from adoption of new accounting pronouncements				0.0
Cash flow hedges:
Unrealized gain		(3.0)	(0.9)	(1.5)	1.8
Reclassification adjustment for losses to net income		(0.2)	(1.1)	(0.5)	(2.5)
Pension plan:
Actuarial loss		(6.5)		(6.5)
Reclassification adjustment to net income for amortization of actuarial loss			0.6	0.3	1.2
Reclassification adjustment to net income for amortization of prior service credits		0.1	(0.4)		(0.7)
Total other comprehensive loss		(24.6)	22.8	(44.7)	24.9
Total comprehensive loss		(401.3)	76.0	(1,554.2)	107.4
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income		(72.9)	96.4	(568.6)	177.0
Other comprehensive income (loss):
Foreign currency translation adjustments		(0.3)		(0.5)
Available-for-sale securities:
Unrealized loss		0.5	0.3	0.3	0.5
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
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 loss		0.2	0.3	(1.0)	0.5
Total comprehensive loss		(72.7)	96.7	(569.6)	177.5
Signet Jewelers Limited | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income		(23.0)	93.4	(519.6)	171.9
Other comprehensive income (loss):
Foreign currency translation adjustments		(15.3)	24.6	(37.0)	25.1
Available-for-sale securities:
Unrealized loss		0.5	0.3	0.3	0.5
Impact from adoption of new accounting pronouncements				(0.8)
Cash flow hedges:
Unrealized gain		(3.0)	(0.9)	(1.5)	1.8
Reclassification adjustment for losses to net income		(0.2)	(1.1)	(0.5)	(2.5)
Pension plan:
Actuarial loss		(6.5)		(6.5)
Reclassification adjustment to net income for amortization of actuarial loss			0.6	0.3	1.2
Reclassification adjustment to net income for amortization of prior service credits		0.1	(0.4)		(0.7)
Total other comprehensive loss		(24.4)	23.1	(45.7)	25.4
Total comprehensive loss		(47.4)	116.5	(565.3)	197.3
Signet UK Finance plc | Reportable Legal Entities
Condensed Statement of Comprehensive Income [Line Items]
Net income		(0.1)	(0.2)	(0.3)	(0.4)
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
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
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 loss				0.0	0.0
Total comprehensive loss		$ (0.1)	$ (0.2)	$ (0.3)	$ (0.4)

[1] During the 13 and 26 weeks ended August 4, 2018, amounts represent unrealized gains related to the Company’s available-for-sale debt securities. During the 13 and 26 weeks ended July 29, 2017, amounts represent 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 available-for-sale equity securities as of February 3, 2018 from AOCI into retained earnings associated with the adoption of ASU 2016-1.