Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

+ Details

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ 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
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cost to be recognized for option under share-based payment arrangement.

+ References

+ Details

Name:	us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ 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
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ 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
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- 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

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

- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of options outstanding, including both vested and non-vested options.

+ 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=116856206&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 2
-Subparagraph (c)(1)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ 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
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis=us-gaap_WarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_TitleOfIndividualAxis=achv_EmployeesAndConsultantsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_TitleOfIndividualAxis=achv_BoardOfDirectorsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=achv_TwoThousandAndEighteenEquityIncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=achv_TwoThousandsAndSeventeenEquityIncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=achv_TwoThousandsAndTenPerformanceIncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Common Stock - Stock Options - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended
	Mar. 31, 2019	Mar. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for options currently outstanding		2,489,426	1,010,583
Unrecognized compensation expense related to stock options granted		$ 2.2
Anti-dilutive securities excluded from earning per share computation	5,038,584	29,615,486
Warrant [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Anti-dilutive securities excluded from earning per share computation		27,116,712
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Anti-dilutive securities excluded from earning per share computation		2,489,426
Restricted Stock Unit [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Anti-dilutive securities excluded from earning per share computation		9,348
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average period, restricted stock awards		2 years 6 months
Stock Options [Member] \| Employees and Consultants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		4 years
Stock Options [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award expiration period		7 years
Stock Options [Member] \| Minimum [Member] \| Board of Directors [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		1 year
Stock Options [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award expiration period		10 years
Stock Options [Member] \| Maximum [Member] \| Board of Directors [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		3 years
Restricted Stock Unit [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		4 years
Common shares reserved for awards currently outstanding		9,348	10,008
Weighted-average period, restricted stock awards		1 year 4 months 2 days
2018 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for issuance under incentive plan		594,209
Award expiration period		10 years
2018 Equity Incentive Plan [Member] \| Minimum [Member] \| Employees and Consultants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		3 years
2018 Equity Incentive Plan [Member] \| Minimum [Member] \| Board of Directors [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		1 year
2018 Equity Incentive Plan [Member] \| Maximum [Member] \| Employees and Consultants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		4 years
2018 Equity Incentive Plan [Member] \| Maximum [Member] \| Board of Directors [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		3 years
2018 Equity Incentive Plan [Member] \| Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for issuance under incentive plan		2,810,314
Common shares reserved for options currently outstanding		2,216,105
2017 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award expiration period		10 years
2017 Equity Incentive Plan [Member] \| Minimum [Member] \| Employees and Consultants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		3 years
2017 Equity Incentive Plan [Member] \| Minimum [Member] \| Board of Directors [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		1 year
2017 Equity Incentive Plan [Member] \| Maximum [Member] \| Employees and Consultants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		4 years
2017 Equity Incentive Plan [Member] \| Maximum [Member] \| Board of Directors [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		3 years
2017 Equity Incentive Plan [Member] \| Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for issuance under incentive plan		267,398
2010 Performance Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award expiration period		10 years
2010 Performance Incentive Plan [Member] \| Minimum [Member] \| Employees and Consultants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		3 years
2010 Performance Incentive Plan [Member] \| Minimum [Member] \| Board of Directors [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		1 year
2010 Performance Incentive Plan [Member] \| Maximum [Member] \| Employees and Consultants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		4 years
2010 Performance Incentive Plan [Member] \| Maximum [Member] \| Board of Directors [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period		3 years
2010 Performance Incentive Plan [Member] \| Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for issuance under incentive plan		15,271
Common shares reserved for options currently outstanding		5,923
2010 Performance Incentive Plan [Member] \| Restricted Stock Unit [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for awards currently outstanding		9,348