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v3.25.2

Segment Information (Details) | 12 Months Ended
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Jun. 30, 2025
Segment Information [Abstract] |
Reportable segment | 1

X
- Definition Number of reportable segments. + References No definition available. + Details
Name: | athe_NumberOfReportableSegment
Namespace Prefix: | athe_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | ifrs-full_DisclosureOfOperatingSegmentsAbstract
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration