Goodwill and intangibles - Summary of Goodwill (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Oct. 28, 2017	Jan. 28, 2017
Goodwill [Roll Forward]
Beginning Balance	$ 517.6	$ 515.5
Impact of foreign exchange	1.0	2.1
Acquisitions	348.5
Ending Balance	867.1	517.6
Sterling Jewelers
Goodwill [Roll Forward]
Beginning Balance	23.2	23.2
Impact of foreign exchange	0.0	0.0
Ending Balance	371.7	23.2
Zale Jewelry
Goodwill [Roll Forward]
Beginning Balance	490.8	488.7
Impact of foreign exchange	1.0	2.1
Acquisitions	0.0
Ending Balance	491.8	490.8
Piercing Pagoda
Goodwill [Roll Forward]
Beginning Balance	0.0	0.0
Impact of foreign exchange	0.0	0.0
Acquisitions	0.0
Ending Balance	0.0	0.0
UK Jewelry
Goodwill [Roll Forward]
Beginning Balance	0.0	0.0
Impact of foreign exchange	0.0	0.0
Acquisitions	0.0
Ending Balance	0.0	0.0
Other
Goodwill [Roll Forward]
Beginning Balance	3.6	3.6
Impact of foreign exchange	0.0	0.0
Acquisitions	0.0
Ending Balance	$ 3.6	$ 3.6

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

+ Details

Name:	us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

+ Details

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

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_GoodwillRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=sig_SterlingJewelersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=sig_ZaleJewelryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=sig_PiercingPagodaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=sig_UKJewelryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_AllOtherSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: