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Common Stock - Employee Share Purchase Plan - Additional Information (Detail) - Employee Share Purchase Plan	9 Months Ended
	Sep. 30, 2022 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum number of shares authorized to purchased	200,000
Number of shares purchased	28,892

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- Definition

Share based compensation, maximum number of shares authorized to purchased.

+ References

No definition available.

+ Details

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Namespace Prefix:	achv_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

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- Definition

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

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Number of shares purchased for issuance under share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (l)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

+ Details

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- Details

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Namespace Prefix:
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