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Segment Information - Narrative (Details)	Dec. 31, 2019 segment
Operating Segments [Abstract]
Number of reporting segments	2

X

- Definition

Number Of Reportable Segments

+ References

No definition available.

+ Details

Name:	alc_NumberOfReportableSegments
Namespace Prefix:	alc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Operating Segments [Abstract]

+ References

No definition available.

+ Details

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