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Common Stock - Employee Share Purchase Plan - Additional Information (Detail) - Employee Share Purchase Plan	3 Months Ended
	Mar. 31, 2022 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum number of shares authorized to purchased	100,000
Number of shares purchased	0

X

- 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

X

- 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901

+ Details

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Balance Type:	na
Period Type:	duration

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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: