Derivatives - Derivative Instruments Designated as Cash Flow Hedges in OCI (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Aug. 04, 2018	Jul. 29, 2017	Aug. 04, 2018	Jul. 29, 2017
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Current period gains (losses) recognized in OCI	$ (4.3)	$ (1.3)	$ (2.4)	$ 3.2
Cash Flow Hedging
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Gains (losses) recorded in AOCI, beginning of period			1.2
Gains recorded in AOCI, end of period	(2.1)	2.3	(2.1)	2.3
Foreign currency contracts \| Cash Flow Hedging
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Gains (losses) recorded in AOCI, beginning of period	(0.8)	2.1	(2.4)	4.1
Current period gains (losses) recognized in OCI	0.8	(0.3)	2.1	(1.3)
Gains recorded in AOCI, end of period	0.4	0.6	0.4	0.6
Commodity contracts \| Cash Flow Hedging
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Gains (losses) recorded in AOCI, beginning of period	1.1	2.1	1.4	(2.1)
Current period gains (losses) recognized in OCI	(5.1)	(0.8)	(4.9)	4.6
Gains recorded in AOCI, end of period	(4.4)	1.0	(4.4)	1.0
Interest Rate Contract \| Cash Flow Hedging
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Gains (losses) recorded in AOCI, beginning of period	2.3	0.8	2.2	0.4
Current period gains (losses) recognized in OCI	0.0	(0.2)	0.4	(0.1)
Gains recorded in AOCI, end of period	1.9	0.7	1.9	0.7
Interest rate swaps \| Cash Flow Hedging
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Gains (losses) recorded in AOCI, beginning of period			2.2
Gains recorded in AOCI, end of period	1.9	0.7	1.9	0.7
Cost of Sales \| Foreign currency contracts \| Cash Flow Hedging
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Gains reclassified from AOCI to net income	0.4	(1.2)	0.7	(2.2)
Cost of Sales \| Commodity contracts \| Cash Flow Hedging
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Gains reclassified from AOCI to net income	(0.4)	(0.3)	(0.9)	(1.5)
Interest expense, net \| Interest Rate Contract \| Cash Flow Hedging
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Gains reclassified from AOCI to net income	$ (0.4)	$ 0.1	$ (0.7)	$ 0.4

Movement in Accumulated Other Comprehensive Income [Roll Forward]

No definition available.

Name:	sig_MovementinAccumulatedOtherComprehensiveIncomeRollForward
Namespace Prefix:	sig_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount before tax of increase (decrease) in accumulated equity from transactions and other events and circumstances from non-owner sources, including portion attributable to noncontrolling interest. Excludes net income (loss), and accumulated changes in equity from transactions resulting from investments by owners (distributions to owners).

+ References

No definition available.

+ Details

Name:	us-gaap_AccumulatedOtherComprehensiveIncomeLossBeforeTax1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624177-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624171-113959

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e637-108580

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109978405&loc=d3e80720-113993

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580

+ Details

Name:	us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_CashFlowHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CommodityContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_CostOfSalesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=us-gaap_InterestExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: