Related parties transactions - Additional information (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Apr. 08, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Related Party [Abstract]
Contract manufacturing revenues from former parent	$ 0		$ 0	$ 47	$ 0
Purchases of the Company from former parent	$ 0		1	$ 19	2
Services received, related party transactions		$ 40	$ 140		$ 276

Related Party [Abstract]

No definition available.

Name:	alc_RelatedPartyAbstract
Namespace Prefix:	alc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Revenue From Contract Manufacturing, Related Party Transactions

+ References

No definition available.

+ Details

Name:	alc_RevenueFromContractManufacturingRelatedPartyTransactions
Namespace Prefix:	alc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of goods purchased by the entity in related party transactions. [Refer: Related parties [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 24
-IssueDate 2018-01-01
-Paragraph 21
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=24&date=2018-03-01&anchor=para_21_a&doctype=Standard
-URIDate 2018-03-16

+ Details

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

- Definition

The amount of services received in related party transactions. [Refer: Related parties [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 24
-IssueDate 2018-01-01
-Paragraph 21
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=24&date=2018-03-01&anchor=para_21_c&doctype=Standard
-URIDate 2018-03-16

+ Details

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