Product Revenue Recognized and Deferred (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Revenues [Line Items]
Product revenue recognized, net	$ 16,480us-gaap_Revenues	$ 14,149us-gaap_Revenues	$ 12,606us-gaap_Revenues	$ 10,967us-gaap_Revenues	$ 10,106us-gaap_Revenues	$ 8,403us-gaap_Revenues	$ 5,500us-gaap_Revenues	$ 2,342us-gaap_Revenues	$ 54,202us-gaap_Revenues	$ 26,351us-gaap_Revenues
Deferred product revenue										1,703us-gaap_DeferredRevenueAdditions
Product Sales, Total									$ 54,202amrn_ProductSales	$ 28,054amrn_ProductSales

Amount of deferred revenue recognized for transactions arising during the current reporting period. Deferred revenue is a liability as of the balance sheet date related to a revenue producing activity for which revenue has not yet been recognized. Generally, an Entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 13.A.4(a).Q1)

-URI http://asc.fasb.org/extlink&oid=27012821&loc=d3e214044-122780

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 13

-Section A

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