Summary of Significant Accounting Policies	6 Months Ended
Summary of Significant Accounting Policies	Jun. 30, 2025
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying condensed consolidated financial statements of the Company for the three and six months ended June 30, 2025 and 2024 are unaudited and have been prepared on a basis substantially consistent with the audited financial statements for the year ended December 31, 2024. The year-end consolidated balance sheet data, which is presented for comparative purposes, was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the U.S. (commonly referred to as “GAAP”). In the opinion of management, the condensed consolidated financial statements include all adjustments of a normal recurring nature that are necessary to state fairly the results of operations for the reported periods. The accompanying condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto of the Company, which are contained in the Annual Report. The results of the Company’s operations for any interim period are not necessarily indicative of the results of the Company’s operations for any other interim period or for any full fiscal year. Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of Alkermes plc and its wholly-owned subsidiaries as disclosed in Note 2, Summary of Significant Accounting Policies in the “Notes to Consolidated Financial Statements” accompanying the Annual Report. Intercompany accounts and transactions have been eliminated. Columns and rows within tables may not sum due to rounding. Discontinued Operations The Company determined that the separation of its oncology business into Mural Oncology plc (“Mural”), a new, independent, publicly-traded company (the “Separation”), completed in November 2023, met the criteria for classification of the oncology business as discontinued operations in accordance with Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 205, Discontinued Operations (“Topic 205”). Use of Estimates The preparation of the Company’s condensed consolidated financial statements in accordance with GAAP requires that Company management make estimates, judgments and assumptions that may affect the reported amounts of assets, liabilities, revenues and expenses, and related disclosure of contingent assets and liabilities. On an ongoing basis, the Company evaluates its estimates, judgments and methodologies, including, but not limited to, those related to revenue from contracts with its customers and related allowances, impairment of long-lived assets, share-based compensation, income taxes including the valuation allowance for deferred tax assets, valuation of investments and litigation. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Actual results may differ from these estimates under different conditions or using different assumptions. Segment Information Operating segments are defined as components of an enterprise engaging in business activities for which separate financial information is available and regularly reviewed by the chief operating decision maker (“CODM”) in deciding how to allocate resources and in assessing performance. The Company has utilized the management approach to determine that the Company is managed as one segment on a consolidated basis and is in the business of developing, manufacturing and commercializing medicines designed to help people living with complex and difficult-to-treat psychiatric and neurological disorders. The Company’s CODM, the Chairman and Chief Executive Officer, reviews the Company’s operating results on an aggregate basis and manages the Company’s operations as a single operating unit. The Company’s CODM measures profitability on a reportable segment basis using net income and utilizes this information in allocating resources and in assessing performance by monitoring budget versus actual results. Please refer to Note 15, Segment Reporting, in these “Notes to Condensed Consolidated Financial Statements” in this Form 10-Q for further information. New Accounting Pronouncements From time to time, new accounting pronouncements are issued by the FASB or other standard-setting bodies that are adopted by the Company on or prior to the specified effective date. Unless otherwise described in this Form 10-Q, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its financial position or results of operations upon adoption. In December 2023, the FASB issued Accounting Standards Update (“ASU”) 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, to enhance the transparency and decision usefulness of income tax disclosures in order to provide information to assist key stakeholders in better assessing how the Company’s operations and related tax risks and tax planning and operational opportunities affect the Company’s tax rate and prospects for future cash flows. This ASU becomes effective for public companies for annual periods beginning after December 15, 2024. This guidance will be applied on a prospective basis. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures. In November 2024, the FASB issued ASU 2024-03, Income Statement - Reporting Comprehensive Income-Expense Disaggregation Disclosures, to improve disclosures about public business entity expenses and address requests from investors for more detailed information about the types of expenses (including purchases of inventory, employee compensation, depreciation, amortization and depletion) in commonly-presented expense captions, such as cost of sales, selling, general and administrative expenses, and research and development. All disclosure requirements under this guidance are required for public business entities and will be effective for annual periods beginning after December 15, 2026 and interim periods beginning after December 15, 2027. Early adoption is permitted and the amendments in this guidance will be applied prospectively to financial statements for periods after the effective dates. The Company is currently evaluating the impact this ASU will have on its consolidated financial statements and related disclosures.