Description of Business and Basis of Presentation	12 Months Ended
Dec. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	1. DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION Alkermes plc is a global biopharmaceutical company that seeks to develop innovative medicines in the field of neuroscience. Alkermes has a portfolio of proprietary commercial products for the treatment of alcohol dependence and opioid dependence, schizophrenia and bipolar I disorder and a pipeline of clinical and preclinical candidates in development for neurological disorders, including narcolepsy and idiopathic hypersomnia. Headquartered in Ireland, Alkermes also has a corporate office and research and development (“R&D”) center in Massachusetts and a manufacturing facility in Ohio. In May 2024, the Company completed the sale of its development and manufacturing facility in Athlone, Ireland (the “Athlone Facility”) and related business to Novo Nordisk (“Novo”) pursuant to an asset purchase agreement entered into in December 2023. The Company and Novo also entered into subcontracting arrangements to continue certain development and manufacturing activities performed at the Athlone Facility for a period of time after the closing of the transaction, which activities may continue through the end of 2025. In connection with the sale of the Athlone Facility, the Company received $97.9 million from Novo, which included a payment of approximately $91.0 million for the facility and certain related assets, and recorded a gain of approximately $1.5 million within “Other income (expense), net” in the accompanying consolidated statements of operations and comprehensive income (loss) for the year ended December 31, 2024. As of December 31, 2023, the Company classified the assets described under the asset purchase agreement for the sale as “Assets held for sale” in the accompanying consolidated balance sheet. In November 2023, the Company completed the separation of its former oncology business into Mural Oncology plc (“Mural”), a new, independent, publicly-traded company (the “Separation”). The Separation was effected by means of a distribution of all of the outstanding ordinary shares of Mural to the Company’s shareholders (the “Distribution”), in which each of the Company’s shareholders received one ordinary share, nominal value $0.01 per share, of Mural for every ten ordinary shares, par value $0.01 per share, of the Company (the “Distribution Ratio”) held by such shareholder as of the close of business on November 6, 2023, the record date for the Distribution (the “Record Date”). The historical results of the oncology business have been reflected as discontinued operations in the Company’s consolidated financial statements through November 15, 2023 (the “Separation Date”). For additional information related to the Separation, see Note 3, Discontinued Operations in these “Notes to Consolidated Financial Statements” in this Annual Report.

Description of Business and Basis of Presentation

12 Months Ended

Dec. 31, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Description of Business and Basis of Presentation

1. DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION

Alkermes plc is a global biopharmaceutical company that seeks to develop innovative medicines in the field of neuroscience. Alkermes has a portfolio of proprietary commercial products for the treatment of alcohol dependence and opioid dependence, schizophrenia and bipolar I disorder and a pipeline of clinical and preclinical candidates in development for neurological disorders, including narcolepsy and idiopathic hypersomnia. Headquartered in Ireland, Alkermes also has a corporate office and research and development (“R&D”) center in Massachusetts and a manufacturing facility in Ohio.

In May 2024, the Company completed the sale of its development and manufacturing facility in Athlone, Ireland (the “Athlone Facility”) and related business to Novo Nordisk (“Novo”) pursuant to an asset purchase agreement entered into in December 2023. The Company and Novo also entered into subcontracting arrangements to continue certain development and manufacturing activities performed at the Athlone Facility for a period of time after the closing of the transaction, which activities may continue through the end of 2025. In connection with the sale of the Athlone Facility, the Company received $97.9 million from Novo, which included a payment of approximately $91.0 million for the facility and certain related assets, and recorded a gain of approximately $1.5 million within “Other income (expense), net” in the accompanying consolidated statements of operations and comprehensive income (loss) for the year ended December 31, 2024. As of December 31, 2023, the Company classified the assets described under the asset purchase agreement for the sale as “Assets held for sale” in the accompanying consolidated balance sheet.

In November 2023, the Company completed the separation of its former oncology business into Mural Oncology plc (“Mural”), a new, independent, publicly-traded company (the “Separation”). The Separation was effected by means of a distribution of all of the outstanding ordinary shares of Mural to the Company’s shareholders (the “Distribution”), in which each of the Company’s shareholders received one ordinary share, nominal value $0.01 per share, of Mural for every ten ordinary shares, par value $0.01 per share, of the Company (the “Distribution Ratio”) held by such shareholder as of the close of business on November 6, 2023, the record date for the Distribution (the “Record Date”). The historical results of the oncology business have been reflected as discontinued operations in the Company’s consolidated financial statements through November 15, 2023 (the “Separation Date”). For additional information related to the Separation, see Note 3, Discontinued Operations in these “Notes to Consolidated Financial Statements” in this Annual Report.