Restructuring plans - Schedule of Plan Liabilities (Details) - USD ($) $ in Millions	12 Months Ended	24 Months Ended
Feb. 01, 2020	Feb. 02, 2019	Feb. 03, 2018	Feb. 01, 2020
Restructuring Reserve [Roll Forward]
Charged to expense	$ 69.9	$ 63.7	$ 0.0
Signet Path to Brillance
Restructuring Reserve [Roll Forward]
Beginning balance	12.6	0.0		$ 0.0
Payments and other adjustments	(79.3)	(113.3)
Charged to expense	79.1	125.9		205.0
Ending balance	12.4	12.6	0.0	12.4
Termination benefits \| Signet Path to Brillance
Restructuring Reserve [Roll Forward]
Beginning balance	0.0	0.0		0.0
Payments and other adjustments	(14.1)	(9.7)
Charged to expense	16.1	9.7		25.8
Ending balance	2.0	0.0	0.0	2.0
Store closure and other costs \| Signet Path to Brillance
Restructuring Reserve [Roll Forward]
Beginning balance	12.6	0.0		0.0
Payments and other adjustments	(65.2)	(103.6)
Charged to expense	63.0	116.2
Ending balance	$ 10.4	$ 12.6	$ 0.0	$ 10.4

Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Section 45
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-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3367-108585

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

+ References

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Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
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