PROVISIONS AND CONTINGENCIES - Changes in provisions (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Changes in Provisions
Provisions at beginning of year	$ 281	$ 326
Net charge to income statement	12	11
Acquisitions		10
Unwinding of discount	3	5
Utilised	(62)	(71)
Transfers	(9)
Exchange adjustment	1
Provisions at end of year	226	281
Rationalisation provisions
Changes in Provisions
Provisions at beginning of year	20	23
Net charge to income statement		12
Utilised	(15)	(14)
Exchange adjustment	1	(1)
Provisions at end of year	6	20
Metal-on-metal
Changes in Provisions
Provisions at beginning of year	163	185
Net charge to income statement	10
Unwinding of discount	3	5
Utilised	(19)	(27)
Provisions at end of year	157	163
Legal and other provisions
Changes in Provisions
Provisions at beginning of year	98	118
Net charge to income statement	2	(1)
Acquisitions		10
Utilised	(28)	(30)
Transfers	(9)
Exchange adjustment		1
Provisions at end of year	$ 63	$ 98

The increase in other provisions resulting from acquisitions through business combinations. [Refer: Business combinations [member]; Other provisions]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 37
-IssueDate 2017-01-01
-Paragraph 84
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2017-03-01&anchor=para_84&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_AcquisitionsThroughBusinessCombinationsOtherProvisions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of additional other provisions made. [Refer: Other provisions]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 37
-IssueDate 2017-01-01
-Paragraph 84
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2017-03-01&anchor=para_84_b&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_AdditionalProvisionsOtherProvisions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) in other provisions resulting from foreign currency exchange rate changes on provisions measured in a currency different from the entity's presentation currency. [Refer: Other provisions]

+ References

+ Details

Name:	ifrs-full_IncreaseDecreaseThroughNetExchangeDifferencesOtherProvisions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase in other provisions through adjustments arising from the passage of time. [Refer: Other provisions]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 37
-IssueDate 2017-01-01
-Paragraph 84
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2017-03-01&anchor=para_84_e&doctype=Standard
-URIDate 2017-03-09

+ Details

Name:	ifrs-full_IncreaseDecreaseThroughTimeValueOfMoneyAdjustmentOtherProvisions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) in other provisions resulting from transfers and changes that the entity does not separately disclose in the same statement or note. [Refer: Other provisions]

+ References

+ Details

Name:	ifrs-full_IncreaseDecreaseThroughTransfersAndOtherChangesOtherProvisions
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount used (ie incurrent and charged against the provision) for other provisions. [Refer: Other provisions]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 37
-IssueDate 2017-01-01
-Paragraph 84
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2017-03-01&anchor=para_84_c&doctype=Standard
-URIDate 2017-03-09

+ Details

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

- Definition

The amount of liabilities of uncertain timing or the amount recognised when: (a) the entity has a present obligation (legal or constructive) as a result of a past event; (b) it is probable (ie more likely than not) that an outflow of resources embodying economic benefits will be required to settle the obligation; and (c) a reliable estimate can be made of the amount of the obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 54
-Subparagraph l
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_54_l&doctype=Standard
-URIDate 2017-03-09

+ Details

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

- References

No definition available.

+ Details

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

- Details

Name:	ifrs-full_ClassesOfProvisionsAxis=ifrs-full_RestructuringProvisionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfProvisionsAxis=snn_MetalOnMetalHipClaimsProvisionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfProvisionsAxis=ifrs-full_LegalProceedingsProvisionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: