| Document and Entity Information - USD ($) $ in Millions | 12 Months Ended | ||
| Dec. 31, 2021 | Apr. 29, 2022 | Jun. 30, 2021 | |
| Document And Entity Information [Line Items] | |||
| Document Type | 10-K/A | ||
| Amendment Flag | true | ||
| Document Period End Date | Dec. 31, 2021 | ||
| Document Fiscal Year Focus | 2021 | ||
| Document Fiscal Period Focus | FY | ||
| Trading Symbol | AMRN | ||
| Entity Registrant Name | AMARIN CORP PLC\UK | ||
| Entity Central Index Key | 0000897448 | ||
| Current Fiscal Year End Date | --12-31 | ||
| Entity Well-known Seasoned Issuer | Yes | ||
| Entity Current Reporting Status | Yes | ||
| Entity Interactive Data Current | Yes | ||
| Entity Voluntary Filers | No | ||
| Entity Filer Category | Large Accelerated Filer | ||
| Entity Emerging Growth Company | false | ||
| Entity Shell Company | false | ||
| Entity Small Business | false | ||
| Entity Public Float | $ 1,710.3 | ||
| Entity File Number | 0-21392 | ||
| Entity Incorporation, State or Country Code | X0 | ||
| Entity Address, Address Line One | 77 Sir John Rogerson’s Quay | ||
| Entity Tax Identification Number | 00-0000000 | ||
| Entity Address, Address Line Two | Block C | ||
| Entity Address, Address Line Three | Grand Canal Docklands | ||
| Entity Address, City or Town | Dublin | ||
| Entity Address, Postal Zip Code | 2 | ||
| Entity Address, Country | IE | ||
| City Area Code | 353 (0) 1 | ||
| Local Phone Number | 6699 020 | ||
| Document Annual Report | true | ||
| Document Transition Report | false | ||
| Title of each class | American Depositary Shares (ADS(s)), each ADS representing the right to receive one (1) Ordinary Share of Amarin Corporation plc | ||
| Name of each exchange on which registered | NASDAQ | ||
| ICFR Auditor Attestation Flag | true | ||
| Documents Incorporated by Reference | DOCUMENTS INCORPORATED BY REFERENCE None. | ||
| Auditor Name | Ernst & Young LLP | ||
| Auditor Firm ID | 42 | ||
| Auditor Location | Iselin, New Jersey | ||
| Amendment Description | EXPLANATORY NOTE Amarin Corporation plc is filing this Amendment No. 1 on Form 10-K/A (this “Amendment”) to its Annual Report on Form 10-K for the fiscal year ended December 31, 2021 (the “Original Form 10-K Filing”), which was originally filed with the Securities and Exchange Commission (the “SEC”) on March 1, 2022, solely to set forth information required by Items 10, 11, 12, 13 and 14 of Part III of Form 10-K. This information was previously omitted from the Original Form 10-K Filing in reliance on General Instruction G.3. to Form 10-K, which permits the above referenced Items to be incorporated in an Annual Report on Form 10-K by reference from a definitive proxy statement which involves the election of directors, if such definitive proxy statement is filed with the SEC no later than 120 days after the end of the fiscal year covered by the Form 10-K. We are filing this Amendment to include the Part III information in our Annual Report on Form 10-K because we no longer intend to file a definitive proxy statement for our annual meeting of shareholders within 120 days after the end of our fiscal year ended December 31, 2021. Accordingly, this Amendment amends and restates in its entirety Items 10, 11, 12, 13 and 14 of Part III of the Original Form 10-K Filing, and the reference on the cover of the Original Form 10-K Filing to the incorporation by reference to portions of our definitive proxy statement into Part III of the Original Form 10-K Filing is hereby deleted. In addition, pursuant to the rules of the SEC, Item 15 of Part IV of the Original Form 10-K Filing is hereby amended solely to include, as Exhibits 31.3 and 31.4, new certifications of our principal executive officer and principal financial officer pursuant to Rule 13a-14(a) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Because no financial statements are included in this Amendment and this Amendment does not contain or amend any disclosure with respect to Items 307 and 308 of Regulation S-K, paragraphs 3, 4, and 5 of such certifications have been omitted. We are not including new certifications required by Rule 13a-14(b) under the Exchange Act as no financial statements are included in this Amendment. Except as described above, no other changes have been made to the Original Form 10-K Filing. The Original Form 10-K Filing continues to speak as of the date of the Original Form 10-K Filing, and we have not updated the disclosures contained therein to reflect any events that have occurred as of a date subsequent to the date of the Original Form 10-K Filing. Accordingly, this Amendment should be read in conjunction with the Original Form 10-K Filing and our other filings made with the SEC subsequent to the filing of the Original Form 10-K Filing. References in this Amendment to “Amarin,” the “Company,” “we,” “our” and “us” refer to Amarin Corporation plc and its subsidiaries, on a consolidated basis, unless otherwise indicated. | ||
| American Depositary Shares | |||
| Document And Entity Information [Line Items] | |||
| Entity Common Stock, Shares Outstanding | 396,811,326 | ||
| Ordinary Shares | |||
| Document And Entity Information [Line Items] | |||
| Entity Common Stock, Shares Outstanding | 196,827 |
