Financial instruments - additional disclosures - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Disclosure of nature and extent of risks arising from financial instruments [line items]
Maximum remaining potential payments related to contingent consideration from business combinations	$ 510
Contingent consideration liabilities [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Purchases, fair value measurement, liabilities	$ 135	$ 102
Adjustments for changes in assumptions		62
Interest rate risk [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Reasonably possible change in risk variable, percent	1.00%
Reasonably possible change in risk variable, impact on loss before taxes	$ 12
Commodity price risk [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Reasonably possible change in risk variable, percent	10.00%
Level 3 [member] \| Contingent consideration liabilities [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Purchases, fair value measurement, liabilities	$ 135	102
Adjustments for changes in assumptions	$ 75	$ 62
Pricing, measurement input [Member] \| Long-term financial investments [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Percentage of possible increase in unobservable input, assets	10.00%
Increase (decrease) in fair value due to increase in unobservable input, assets	$ 3
Percentage of reasonably possible decrease in unobservable input, assets	10.00%
Increase (decrease) in fair value measurement due to reasonably possible decrease in unobservable input, recognised in other comprehensive income, before tax, assets	$ 3
Significant parameters, measurement input [Member] \| Contingent consideration liabilities [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Percentage of possible increase in unobservable input, liabilities	10.00%
Increase (decrease) in fair value due to possible increase in unobservable input, recognised in profit or loss, before tax, liabilities	$ 34
Percentage of reasonably possible decrease in unobservable input, liabilities	10.00%
Increase (decrease) in fair value measurement due to reasonably possible decrease in unobservable input, recognised in profit or loss, before tax, liabilities	$ 34
Probability of success, measurement input [Member] \| Contingent consideration liabilities [member]
Disclosure of nature and extent of risks arising from financial instruments [line items]
Percentage of possible increase in unobservable input, liabilities	10.00%
Increase (decrease) in fair value due to possible increase in unobservable input, recognised in profit or loss, before tax, liabilities	$ 32
Percentage of reasonably possible decrease in unobservable input, liabilities	10.00%
Increase (decrease) in fair value measurement due to reasonably possible decrease in unobservable input, recognised in profit or loss, before tax, liabilities	$ 32

Adjustments, Fair Value Measurement, Liabilities

No definition available.

Name:	alc_AdjustmentsFairValueMeasurementLiabilities
Namespace Prefix:	alc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Impact On Pre-Tax Earnings

+ References

No definition available.

+ Details

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

- Definition

Sensitivity Analysis For Types Of Market Risk, Reasonably Possible Change In Risk Variable, Percent

+ References

No definition available.

+ Details

Name:	alc_SensitivityAnalysisForTypesOfMarketRiskReasonablyPossibleChangeInRiskVariablePercent
Namespace Prefix:	alc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

+ References

No definition available.

+ Details

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

- Definition

The amount of the estimated financial effect of contingent liabilities in a business combination that were not recognised because their fair value cannot be measured reliably. [Refer: Contingent liabilities [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 3
-IssueDate 2019-01-01
-Paragraph B64
-Subparagraph j
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=3&code=ifrs-tx-2019-en-r&anchor=para_B64_j_i&doctype=Appendix&subtype=B
-URIDate 2019-03-27

+ Details

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

- Definition

The amount of increase (decrease) in the fair value measurement of assets, recognised in other comprehensive income before tax, due to a reasonably possible decrease in an unobservable input. [Refer: Tax income (expense)]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 13
-IssueDate 2019-01-01
-Paragraph 93
-Subparagraph h
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=13&code=ifrs-tx-2019-en-r&anchor=para_93_h_ii&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_IncreaseDecreaseInFairValueMeasurementDueToReasonablyPossibleDecreaseInUnobservableInputRecognisedInOtherComprehensiveIncomeBeforeTaxAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of increase (decrease) in the fair value measurement of liabilities, recognised in profit or loss before tax, due to a reasonably possible decrease in an unobservable input. [Refer: Tax income (expense)]

+ References

+ Details

Name:	ifrs-full_IncreaseDecreaseInFairValueMeasurementDueToReasonablyPossibleDecreaseInUnobservableInputRecognisedInProfitOrLossBeforeTaxLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of increase (decrease) in the fair value measurement of assets, recognised in other comprehensive income before tax, due to a reasonably possible increase in an unobservable input. [Refer: Tax income (expense)]

+ References

+ Details

Name:	ifrs-full_IncreaseDecreaseInFairValueMeasurementDueToReasonablyPossibleIncreaseInUnobservableInputRecognisedInOtherComprehensiveIncomeBeforeTaxAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of increase (decrease) in the fair value measurement of liabilities, recognised in profit or loss before tax, due to a reasonably possible increase in an unobservable input. [Refer: Tax income (expense)]

+ References

+ Details

Name:	ifrs-full_IncreaseDecreaseInFairValueMeasurementDueToReasonablyPossibleIncreaseInUnobservableInputRecognisedInProfitOrLossBeforeTaxLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of a reasonably possible decrease in an unobservable input used in fair value measurement of assets.

+ References

+ Details

Name:	ifrs-full_PercentageOfReasonablyPossibleDecreaseInUnobservableInputAssets
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of a reasonably possible decrease in an unobservable input used in fair value measurement of liabilities.

+ References

+ Details

Name:	ifrs-full_PercentageOfReasonablyPossibleDecreaseInUnobservableInputLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of a reasonably possible increase in an unobservable input used in fair value measurement of assets.

+ References

+ Details

Name:	ifrs-full_PercentageOfReasonablyPossibleIncreaseInUnobservableInputAssets
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of a reasonably possible increase in an unobservable input used in fair value measurement of liabilities.

+ References

+ Details

Name:	ifrs-full_PercentageOfReasonablyPossibleIncreaseInUnobservableInputLiabilities
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The increase in the fair value measurement of liabilities resulting from purchases of those liabilities. [Refer: At fair value [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 13
-IssueDate 2019-01-01
-Paragraph 93
-Subparagraph e
-Clause iii
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=13&code=ifrs-tx-2019-en-r&anchor=para_93_e_iii&doctype=Standard
-URIDate 2019-03-27

+ Details

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

- Details

Name:	ifrs-full_ClassesOfFinancialLiabilitiesAxis=alc_FinancialLiabilitiesContingentConsiderationLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TypesOfRisksAxis=ifrs-full_InterestRateRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_TypesOfRisksAxis=ifrs-full_CommodityPriceRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_LevelsOfFairValueHierarchyAxis=ifrs-full_Level3OfFairValueHierarchyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_UnobservableInputsAxis=alc_PricingMeasurementInputMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_ClassesOfFinancialAssetsAxis=alc_FinancialAssetsLongtermFinancialInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_UnobservableInputsAxis=alc_SignificantParametersMeasurementInputMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_UnobservableInputsAxis=alc_ProbabilityOfSuccessMeasurementInputMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: