Area under sub-lease agreement.

No definition available.

Name:	amrn_AreaUnderSubLeaseAgreement
Namespace Prefix:	amrn_
Data Type:	dtr-types:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Lease operating sublease commencement date.

+ References

No definition available.

+ Details

Name:	amrn_LeaseOperatingSubleaseCommencementDate
Namespace Prefix:	amrn_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of renewal options.

+ References

No definition available.

+ Details

Name:	amrn_NumberOfRenewalOptions
Namespace Prefix:	amrn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Operating lease change in weighted average discount rate percent.

+ References

No definition available.

+ Details

Name:	amrn_OperatingLeaseChangeInWeightedAverageDiscountRatePercent
Namespace Prefix:	amrn_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Operating lease commencement date.

+ References

No definition available.

+ Details

Name:	amrn_OperatingLeaseCommencementDate
Namespace Prefix:	amrn_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Operating lease termination date.

+ References

No definition available.

+ Details

Name:	amrn_OperatingLeaseTerminationDate
Namespace Prefix:	amrn_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Short term lease period.

+ References

No definition available.

+ Details

Name:	amrn_ShortTermLeasePeriod
Namespace Prefix:	amrn_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Area of land held.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfLand
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

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

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-7A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-3

+ Details

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

- Definition

Description of lessee's operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-3

+ Details

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

- Definition

Indicates (true false) whether lessee has option to terminate operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-3

+ Details

Name:	us-gaap_LesseeOperatingLeaseExistenceOfOptionToTerminate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477314/942-235-S99-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-4

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-3

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-6

+ Details

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

- Definition

Description of terms and conditions of option to terminate lessee's operating lease. Includes, but is not limited to, information about option recognized as part of right-of-use asset and lease liability.

+ References

+ Details

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

- Definition

Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-3

+ Details

Name:	us-gaap_LesseeOperatingLeaseRenewalTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

+ Details

Name:	us-gaap_LesseeOperatingLeaseTermOfContract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of lease payments to be received by lessor for operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479773/842-30-50-12

+ Details

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

- Definition

Amount of operating lease expense. Excludes sublease income.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 4
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-4

+ Details

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

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-1

+ Details

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

- Definition

Amount of lessee's right to use underlying asset under operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-1

+ Details

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

- Definition

Weighted average discount rate for operating lease calculated at point in time.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 53
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479589/842-20-55-53

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (g)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-4

+ Details

Name:	us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	amrn_LocationAxis=amrn_BridgewaterMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	amrn_LocationAxis=amrn_ZugSwitzerlandMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	amrn_LocationAxis=amrn_DublinMember
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_PropertyPlantAndEquipmentByTypeAxis=us-gaap_VehiclesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Leases - Additional Information (Detail) $ in Thousands							3 Months Ended		6 Months Ended
Leases - Additional Information (Detail) $ in Thousands	Mar. 01, 2025 USD ($)	Sep. 01, 2024 USD ($)	Feb. 01, 2023 USD ($)	Oct. 01, 2022 USD ($)	Feb. 01, 2022 USD ($) RenewalOption	Aug. 15, 2019 USD ($) RenewalOption	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)	Sep. 30, 2024 USD ($)	Jan. 20, 2023 ft²
Lessee Lease Description [Line Items]
Incremental borrowing rate for purposes of calculation of lease liabilities							11.50%		11.50%
Change in incremental borrowing rate									1.00%
Rent payment							$ 12,194		$ 12,194
Operating lease liability							9,600		9,600		$ 9,700
Operating lease right-of-use asset							7,640		7,640		$ 7,592
Operating lease expense							$ 900	$ 800	$ 1,800	$ 1,700
Receive rent payment												$ 5,612
Bridgewater
Lessee Lease Description [Line Items]
Lease commencement date						Aug. 15, 2019
Lease agreement term			7 years 6 months			11 years
Number of renewal options \| RenewalOption						2
Lease renewal term						5 years
Description of lease agreement									will have a one-time option to terminate the agreement effective on the first day of the 97th month after the Commencement Date upon advance written notice and a termination payment specified in the Lease.
Lease termination description									one-time option to terminate the agreement effective on the first day of the 97th month after the Commencement Date
Lease termination existence of option to extend						true
Rent payment						$ 100
Area under sub-lease agreement \| ft²													50,000
Lease agreement area \| ft²													67,747
Sublease commencement date			Feb. 01, 2023
Receive rent payment			$ 100
Zug Switzerland
Lessee Lease Description [Line Items]
Lease commencement date					Feb. 01, 2022
Lease agreement term					5 years
Number of renewal options \| RenewalOption					1
Lease renewal term					5 years
Rent payment					$ 200
Dublin
Lessee Lease Description [Line Items]
Lease commencement date	Mar. 01, 2025	Sep. 01, 2024		Oct. 01, 2022
Lease agreement term	2 years	2 years		2 years
Rent payment	$ 900	$ 500		$ 400
Lease termination date		Feb. 28, 2025
Maximum
Lessee Lease Description [Line Items]
Short term lease period									12 months
Maximum \| Vehicles
Lessee Lease Description [Line Items]
Lease agreement term							36 months		36 months