Summarizes Activity of the Net Product Revenue Allowance and Reserve Categories (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	$ 7,090	$ 2,469
Provision related to current period and deferred sales	56,229	32,460
Provision related to prior period sales	(449)	(128)
Credits/payments made for current period and deferred sales	(40,626)	(25,431)
Credits/payments made for prior period sales	(6,448)	(2,280)
Ending balance	15,796	7,090
Trade Receivables
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	2,207	1,071
Provision related to current period and deferred sales	14,986	8,157
Provision related to prior period sales	(174)	(29)
Credits/payments made for current period and deferred sales	(10,690)	(5,950)
Credits/payments made for prior period sales	(2,033)	(1,042)
Ending balance	4,296	2,207
Rebates Chargebacks And Discounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	3,610	1,137
Provision related to current period and deferred sales	32,591	12,753
Provision related to prior period sales	(70)	(80)
Credits/payments made for current period and deferred sales	(22,710)	(9,143)
Credits/payments made for prior period sales	(3,540)	(1,057)
Ending balance	9,881	3,610
Allowance for Sales Returns
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	481	72
Provision related to current period and deferred sales	342	397
Provision related to prior period sales	(205)	12
Credits/payments made for prior period sales	(83)
Ending balance	535	481
Other Incentive Programs
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning balance	792	189
Provision related to current period and deferred sales	8,310	11,153
Provision related to prior period sales		(31)
Credits/payments made for current period and deferred sales	(7,226)	(10,338)
Credits/payments made for prior period sales	(792)	(181)
Ending balance	$ 1,084	$ 792

Credits/payments Made for Prior Period Sales

No definition available.

Name:	amrn_CreditsPaymentsMadeForPriorPeriodSales
Namespace Prefix:	amrn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Provision Related to Prior Period Sales

+ References

No definition available.

+ Details

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

- Definition

Total of allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 09
-Article 12

+ Details

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

- Definition

+ References

+ Details

Name:	us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Total of the deductions in a given period to allowances and reserves, the valuation and qualifying accounts that are either netted against the cost of an asset (in order to value it at its carrying value) or that reflect a liability established to represent expected future costs, representing receivables written off as uncollectible and portions of the reserves utilized, respectively.

+ References

+ Details

Name:	us-gaap_ValuationAllowancesAndReservesDeductions
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

No definition available.

+ Details

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

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=us-gaap_AllowanceForTradeReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=amrn_RebatesChargebacksAndDiscountsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=us-gaap_AllowanceForSalesReturnsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=amrn_OtherIncentiveProgramsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: