Development, Commercialization and Supply Agreement - Recognized Revenues Changes in Contract Asset and Contract Liability Balances (Detail) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2022	Jun. 30, 2021
Revenue recognized in the period from:
Amounts included in contract liability at the beginning of the period	$ 701	$ 662

Contract with customer liability revenue recognized excluding performance obligation satisfied in previous period.

No definition available.

Name:	amrn_ContractWithCustomerLiabilityRevenueRecognizedExcludingPerformanceObligationSatisfiedInPreviousPeriod
Namespace Prefix:	amrn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration