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Other Assets - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Period of not utilizing deferred share issuance costs and prepaid amounts related to insurance	12 months

X

- Definition

Period of not utilizing deferred share issuance costs and prepaid amounts related to insurance.

+ References

No definition available.

+ Details

Name:	achv_PeriodOfNotUtilizingDeferredShareIssuanceCostsAndPrepaidAmountsRelatedToInsurance
Namespace Prefix:	achv_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- References

No definition available.

+ Details

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