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Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions |  | 9 Months Ended
--- | --- | ---
Aug. 01, 2021 | Sep. 30, 2021
NIDA |  |
Accounting Policies [Line Items] |  |
Grant received | $ 0.3 |
NIH Grant |  |
Accounting Policies [Line Items] |  |
Reduction in R&D expense |  | $ 0.2
Grant receivable |  | $ 0.2

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- Definition Accounting policies. + References No definition available. + Details
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Namespace Prefix: | achv_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Grant received. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Research and development expenses increase (decrease). + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Carrying amount as of the balance sheet date of amounts due under the terms of governmental, corporate, or foundation grants. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.8) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Details
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- Details
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