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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

X

- 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

X

- Definition

Grant received.

+ References

No definition available.

+ Details

Name:	achv_GrantReceived
Namespace Prefix:	achv_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Research and development expenses increase (decrease).

+ References

No definition available.

+ Details

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Namespace Prefix:	achv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- 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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RegulatoryAgencyAxis=achv_NationalInstitutesOfHealthResearchGrantMember
Namespace Prefix:
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Balance Type:
Period Type: