Commitments and contingencies.

No definition available.

Name:	amlx_CommitmentsAndContingenciesLineItems
Namespace Prefix:	amlx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum royalty guarantees commitments amount payable to each grantor.

+ References

No definition available.

+ Details

Name:	amlx_MaximumRoyaltyGuaranteesCommitmentsAmountPayableToEachGrantor
Namespace Prefix:	amlx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of operating lease agreements.

+ References

No definition available.

+ Details

Name:	amlx_NumberOfOperatingLeaseAgreements
Namespace Prefix:	amlx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Royalty guarantees commitments annual installment payment, percentage of net sales of products developed under project.

+ References

No definition available.

+ Details

Name:	amlx_RoyaltyGuaranteesCommitmentsAnnualInstallmentPaymentPercentageOfNetSalesOfProductsDevelopedUnderProject
Namespace Prefix:	amlx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Royalty guarantees commitments, percentage of all royalties and cash proceeds from revenue generating transaction associated with project.

+ References

No definition available.

+ Details

Name:	amlx_RoyaltyGuaranteesCommitmentsPercentageOfAllRoyaltiesAndCashProceedsFromRevenueGeneratingTransactionAssociatedWithProject
Namespace Prefix:	amlx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Royalty guarantees commitments percentage of annual net sales of products commercialized from project.

+ References

No definition available.

+ Details

Name:	amlx_RoyaltyGuaranteesCommitmentsPercentageOfAnnualNetSalesOfProductsCommercializedFromProject
Namespace Prefix:	amlx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Royalty guarantees commitments, percentage of cash proceeds from revenue generating transaction under project.

+ References

No definition available.

+ Details

Name:	amlx_RoyaltyGuaranteesCommitmentsPercentageOfCashProceedsFromRevenueGeneratingTransactionUnderProject
Namespace Prefix:	amlx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Royalty guarantees commitments percentage of grant received payable to each guarantor.

+ References

No definition available.

+ Details

Name:	amlx_RoyaltyGuaranteesCommitmentsPercentageOfGrantReceivedPayableToEachGuarantor
Namespace Prefix:	amlx_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash received from grantors during the current period related to operating activities. This element represents receipts from a guarantor for the amount of guarantee provided.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3536-108585

+ Details

Name:	us-gaap_ProceedsFromGrantors
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cash restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 8
-URI https://asc.fasb.org/extlink&oid=126999549&loc=SL98516268-108586

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 954
-SubTopic 210
-Section 45
-Paragraph 5
-URI https://asc.fasb.org/extlink&oid=120413173&loc=SL116631458-115580

+ Details

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

- Definition

Amount of expense related to royalty payments under a contractual arrangement such as payment for mineral and drilling rights and use of technology or intellectual property.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI https://asc.fasb.org/extlink&oid=126953954&loc=SL114868664-224227

+ Details

Name:	us-gaap_RoyaltyExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount the entity has committed to make for future royalty guarantees.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 928
-SubTopic 440
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6473578&loc=d3e63223-108013

+ Details

Name:	us-gaap_RoyaltyGuaranteesCommitmentsAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	srt_CounterpartyNameAxis=amlx_ALSAssociationAndALSFindingCureMember
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_IncomeStatementLocationAxis=us-gaap_CostOfSalesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis=us-gaap_RoyaltyAgreementTermsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=amlx_AlzheimersDrugDiscoveryFoundationAlzheimersAssociationAndCureAlzheimersFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnderlyingAssetClassAxis=us-gaap_CollateralizedDebtObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_UnderlyingAssetClassAxis=us-gaap_CollateralizedCreditCardSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commitment and Contingencies - Additional Information (Details)	3 Months Ended	9 Months Ended	31 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2022 USD ($) LeaseAgreement	Feb. 28, 2019 USD ($)	Dec. 31, 2021 USD ($)
Commitments And Contingencies [Line Items]
Number of operating lease agreements \| LeaseAgreement		2
Restricted cash	$ 719,000	$ 719,000		$ 189,000
ALS Association and ALS Finding a Cure \| Maximum \| Cost of Sales
Commitments And Contingencies [Line Items]
Royalty expense	100,000	100,000
Royalty Payments Agreements with Grantors
Commitments And Contingencies [Line Items]
Proceeds from grants			$ 4,300,000
Royalty Payments Agreements with Grantors \| ALS Association and ALS Finding a Cure
Commitments And Contingencies [Line Items]
Percentage of grant received			150.00%
Percentage of net sales of products developed under projects			3.00%
Percentage of cash proceeds from revenue generating transaction			3.00%
Royalty Payments Agreements with Grantors \| Alzheimer's Drug Discovery Foundation, the Alzheimer's Association, and Cure Alzheimer's Fund
Commitments And Contingencies [Line Items]
Maximum Royalty amount payable to each grantor			$ 15,000,000.0
Aggregate royalty amount payable to grantor			$ 45,000,000.0
Percentage of annual net sales of products commercialized from project			4.00%
Percentage of all royalties and cash proceeds from revenue generating transaction			15.00%
Collateral for Letter of Credit Issued
Commitments And Contingencies [Line Items]
Restricted cash	200,000	200,000
Collateral for Corporate Credit Card Program
Commitments And Contingencies [Line Items]
Restricted cash	$ 500,000	$ 500,000