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Subsequent Events - Additional Information (Detail) - LPC [Member] - Purchase Agreement [Member] - USD ($) | Mar. 12, 2020 | Sep. 14, 2017
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Subsequent Event [Line Items] |  |
Additional purchase of common stock |  | 80,000
Subsequent Event [Member] |  |
Subsequent Event [Line Items] |  |
Agreement term | 30 months |
Agreement extended term | 54 months |
Additional purchase of common stock | 150,000 |
Payments related to expense reimbursement | $ 100,000 |

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- Definition Agreement extended term. + References No definition available. + Details
Name: | achv_AgreementExtendedTerm
Namespace Prefix: | achv_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Agreement term. + References No definition available. + Details
Name: | achv_AgreementTerm
Namespace Prefix: | achv_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Payments related to expense reimbursement. + References No definition available. + Details
Name: | achv_PaymentsRelatedToExpenseReimbursement
Namespace Prefix: | achv_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Sale of stock number of additional shares to be issued in transaction. + References No definition available. + Details
Name: | achv_SaleOfStockNumberOfAdditionalSharesToBeIssuedInTransaction
Namespace Prefix: | achv_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

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- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_CounterpartyNameAxis=achv_LincolnParkCapitalFundLimitedLiabilityCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_TypeOfArrangementAxis=achv_PurchaseAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |