INVESTMENTS IN ASSOCIATES - Summarised balance sheet (Details) $ in Millions	12 Months Ended	24 Months Ended
Dec. 31, 2018 USD ($) item	Dec. 31, 2017 USD ($) item	Dec. 31, 2018 USD ($) item
Summarised balance sheet
Non-current assets	$ 4,982	$ 5,135	$ 4,982
Current assets	3,077	2,731	3,077
Non-current liabilities	(1,720)	(1,876)	(1,720)
Current liabilities	(1,465)	(1,346)	(1,465)
Group's carrying amount of investment	$ 105	$ 118	$ 105
Number of associates \| item	1	1	1
Bioventus
Summarised balance sheet
Non-current assets	$ 296	$ 332	$ 296
Current assets	149	122	149
Non-current liabilities	(234)	(246)	(234)
Current liabilities	(56)	(47)	(56)
Net assets	155	161	155
Group's share of net assets	76	79	76
Group adjustments	26	35	26
Group's carrying amount of investment	102	114	$ 102
Percentage of associate held			49.00%
Cash distribution received	2	0
Other associates
Summarised balance sheet
Group's carrying amount of investment	$ 3	$ 3	$ 3

The amount of assets that the entity (a) expects to realise or intends to sell or consume in its normal operating cycle; (b) holds primarily for the purpose of trading; (c) expects to realise within twelve months after the reporting period; or (d) classifies as cash or cash equivalents (as defined in IAS 7) unless the asset is restricted from being exchanged or used to settle a liability for at least twelve months after the reporting period. [Refer: Assets]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B12
-Subparagraph b
-Clause i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B12_b_i&doctype=Appendix&seq=2
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 66
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_66&doctype=Standard
-URIDate 2018-03-16

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B10
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B10_b&doctype=Appendix&seq=2
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_CurrentAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of liabilities that: (a) the entity expects to settle in its normal operating cycle; (b) the entity holds primarily for the purpose of trading; (c) are due to be settled within twelve months after the reporting period; or (d) the entity does not have an unconditional right to defer settlement for at least twelve months after the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B12
-Subparagraph b
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B12_b_iii&doctype=Appendix&seq=2
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 69
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_69&doctype=Standard
-URIDate 2018-03-16

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B10
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B10_b&doctype=Appendix&seq=2
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_CurrentLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of dividends received.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B12
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B12_a&doctype=Appendix&seq=2
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_DividendsReceived
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of investments in associates accounted for using the equity method. [Refer: Associates [member]; Investments accounted for using equity method]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_55&doctype=Standard
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_InvestmentsInAssociatesAccountedForUsingEquityMethod
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of assets less the amount of liabilities.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 1
-IssueDate 2018-01-01
-Paragraph IG63
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=1&date=2018-03-01&anchor=para_IG63&doctype=Implementation%20Guidance
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 112
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_112_c&doctype=Standard
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_NetAssetsLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of assets that do not meet the definition of current assets. [Refer: Current assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 66
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_66&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B12
-Subparagraph b
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B12_b_ii&doctype=Appendix&seq=2
-URIDate 2018-03-16

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B10
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B10_b&doctype=Appendix&seq=2
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_NoncurrentAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of liabilities that do not meet the definition of current liabilities. [Refer: Current liabilities]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B12
-Subparagraph b
-Clause iv
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B12_b_iv&doctype=Appendix&seq=2
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 69
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_69&doctype=Standard
-URIDate 2018-03-16

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B10
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B10_b&doctype=Appendix&seq=2
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_NoncurrentLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The proportion of ownership interest in an associate attributable to the entity. [Refer: Associates [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2018-01-01
-Paragraph 17
-Subparagraph b
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=27&date=2018-03-01&anchor=para_17_b_iii&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2018-01-01
-Paragraph 16
-Subparagraph b
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=27&date=2018-03-01&anchor=para_16_b_iii&doctype=Standard
-URIDate 2018-03-16

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph 21
-Subparagraph a
-Clause iv
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_21_a_iv&doctype=Standard
-URIDate 2018-03-16

+ Details

Name:	ifrs-full_ProportionOfOwnershipInterestInAssociate
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	ifrs-full_StatementOfFinancialPositionAbstract
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Adjustments to align the reported amount of net assets of associates accounted for using equity method with the entity's policy for reporting.

+ References

No definition available.

+ Details

Name:	snn_CumulativeAdjustmentsToNetAssetsOfAssociatesAccountedForUsingEquityMethod
Namespace Prefix:	snn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The number of additional associates in which the entity reports an equity method investment.

+ References

No definition available.

+ Details

Name:	snn_NumberOfAssociates
Namespace Prefix:	snn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The entity's share of assets from continuing operations of associates and joint ventures accounted for using the equity method.

+ References

No definition available.

+ Details

Name:	snn_ShareOfAssetsOfAssociatesAndJointVenturesAccountedForUsingEquityMethod
Namespace Prefix:	snn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	ifrs-full_SignificantInvestmentsInAssociatesAxis=snn_BioventusLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SignificantInvestmentsInAssociatesAxis=ifrs-full_AggregatedIndividuallyImmaterialAssociatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: