Fair Value Measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Marketable securities
Total fair value	$ 216,070	$ 224,856
Fair Value, Inputs, Level 1 [Member]
Marketable securities
Total fair value	108,086	121,162
Fair Value, Inputs, Level 2 [Member]
Marketable securities
Total fair value	107,984	103,694
Fair Value, Inputs, Level 3 [Member]
Marketable securities
Total fair value	0	0
Money Market Securities [Member]
Cash and cash equivalents
Cash and Cash Equivalents, Fair Value Disclosure	108,086	121,162
Money Market Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents
Cash and Cash Equivalents, Fair Value Disclosure	108,086	121,162
Money Market Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Money Market Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Commercial Paper [Member]
Marketable securities
Investments, Fair Value Disclosure	47,961	47,939
Commercial Paper [Member] \| Fair Value, Inputs, Level 1 [Member]
Marketable securities
Investments, Fair Value Disclosure	0
Commercial Paper [Member] \| Fair Value, Inputs, Level 2 [Member]
Marketable securities
Investments, Fair Value Disclosure	47,961	47,939
Commercial Paper [Member] \| Fair Value, Inputs, Level 3 [Member]
Marketable securities
Investments, Fair Value Disclosure	0
Corporate Debt Securities [Member]
Marketable securities
Investments, Fair Value Disclosure	24,304	24,694
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Marketable securities
Investments, Fair Value Disclosure	0
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Marketable securities
Investments, Fair Value Disclosure	24,304	24,694
Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Marketable securities
Investments, Fair Value Disclosure	0
Asset-backed Securities [Member]
Marketable securities
Investments, Fair Value Disclosure	14,958	19,143
Asset-backed Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Marketable securities
Investments, Fair Value Disclosure	0
Asset-backed Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Marketable securities
Investments, Fair Value Disclosure	14,958	19,143
Asset-backed Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Marketable securities
Investments, Fair Value Disclosure	0
US Treasury Securities [Member]
Marketable securities
Investments, Fair Value Disclosure	20,761	11,918
US Treasury Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Marketable securities
Investments, Fair Value Disclosure	0
US Treasury Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Marketable securities
Investments, Fair Value Disclosure	20,761	$ 11,918
US Treasury Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Marketable securities
Investments, Fair Value Disclosure	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

No definition available.

+ Details

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

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

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

- References

No definition available.

+ Details

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

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=abos_MoneyMarketSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: