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Common Stock - Common Stock Warrants - Additional Information (Detail) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of warrants exercised	0	0

X

- Definition

Number of warrants exercised.

+ References

No definition available.

+ Details

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

X

- References

No definition available.

+ Details

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