| Document and Entity Information | 12 Months Ended |
| Dec. 31, 2023 | |
| Cover [Abstract] | |
| Document Type | PRE 14A |
| Amendment Flag | false |
| Entity Registrant Name | ALKERMES PLC |
| Entity Central Index Key | 0001520262 |
| Pay vs Performance Disclosure - USD ($) | 12 Months Ended | |||
| Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | |
| Pay vs Performance Disclosure | ||||
| Pay vs Performance Disclosure, Table | Pay Versus Performance The disclosure included in this section is prescribed by SEC rules and does not necessarily align with how our Company or the Compensation Committee view the link between Company performance and executive compensation for our principal executive officer (“PEO”) and our non-PEO NEOs. For additional information about our pay-for-performance philosophy and how we align executive compensation with Company performance, see our Compensation Discussion and Analysis beginning on page 82 of this proxy statement. Required Tabular Disclosure of Pay Versus Performance The amounts set forth below under the headings “Compensation Actually Paid to PEO” and “Average Compensation Actually Paid to Non-PEO NEOs” have been calculated in a manner consistent with Item 402(v) of Regulation S-K. Use of the term “compensation actually paid” is required by the SEC’s rules and, as a result of the calculation methodology required by the SEC, such amounts differ from compensation actually earned, realized or received by the individuals and the compensation decisions described in our Compensation Discussion and Analysis beginning on page 82 of this proxy statement. Summary Compensation Average Average Value of Initial Fixed $ (3) Year Compensation (1) Actually (1)(2) Table Total (1) Paid to (1)(2) TSR Peer Group GAAP Net Income (Loss) Non-GAAP (4) ($ Millions) (a) (b) (c) (d) (e) (f) (g) (h) (i) 2023 9,442,066 8,983,892 4,033,464 4,190,097 138.19 118.87 355.8 243.7 2022 10,314,172 8,321,591 4,155,421 4,206,760 128.09 113.65 ( 158.3 ) 57.9 2021 8,846,588 11,225,263 2,942,671 2,882,217 114.02 126.45 ( 48.2 ) 129.1 2020 8,041,702 6,883,292 2,882,616 2,656,656 97.79 126.42 ( 110.9 ) 68.6 (1) Richard F. Pops was our PEO for each year presented. The individuals comprising the non-PEO NEOs for each year presented are listed below. 2020 2021 2022 2023 James M. Frates Iain M. Brown Iain M. Brown Iain M. Brown David J. Gaffin James M. Frates David J. Gaffin David J. Gaffin Craig C. Hopkinson, M.D. David J. Gaffin Craig C. Hopkinson, M.D. Craig C. Hopkinson, M.D. Michael J. Landine Craig C. Hopkinson, M.D. Blair C. Jackson Blair C. Jackson Blair C. Jackson (2) For 2023, the amounts shown reflect the exclusion and inclusion of those certain amounts for the PEO and the non-PEO NEOs shown in the following tables. Equity values are calculated in accordance with ASC 718. Amounts shown in each of the Exclusion of Stock Awards and Option Awards columns are equal to the total amounts from the Stock Awards and Option Awards columns set forth in the Summary Compensation Table on page 112 of this proxy statement. See the section entitled “Pay Versus Performance” on page 130 of the proxy statement for the 2023 Annual Meeting for the adjustments made to determine compensation actually paid amounts for prior years. Year Summary Compensation Table Total for PEO Exclusion of Stock Awards and Option Awards for PEO Inclusion of Equity Values for PEO Compensation Actually Paid to PEO 2023 9,442,066 ( 6,831,832 ) 6,373,658 8,983,892 Year Average Summary Compensation Table Total for Non-PEO NEOs Average Exclusion of Stock Awards and Option Awards for Non-PEO NEOs Average Inclusion of Equity Values for Non-PEO NEOs Average Compensation Actually Paid to Non-PEO NEOs 2023 4,033,464 ( 2,902,745 ) 3,059,378 4,190,097 The amounts shown in the Inclusion of Equity Values column in each of the above tables are derived from the following amounts: Year Year-End Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year for PEO Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards for PEO Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards that Vested During Year for PEO Fair Value at Last Day of Prior Year of Equity Awards Forfeited During Year for PEO Total - Inclusion of Equity Values for PEO 2023 3,934,846 2,022,849 415,963 — 6,373,658 Year Average Year-End Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year for Non-PEO NEOs Average Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards for Non-PEO NEOs Average Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards that Vested During Year for Non-PEO NEOs Average Fair Value at Last Day of Prior Year of Equity Awards Forfeited During Year for Non-PEO NEOs Total - Average Inclusion of Equity Values for Non-PEO NEOs 2023 2,453,179 437,482 168,717 — 3,059,378 (3) The peer group TSR shown in this table utilizes the Nasdaq Biotechnology Index (also known as the IBB Index ), which we also utilize in the stock performance graph required by Item 201(e) of Regulation S-K included in our Annual Report. The comparison assumes $100 was invested in the Company and in the Nasdaq Biotechnology Index , respectively, for the period starting December 31, 2019 through the end of the year shown. Historical share price performance is not necessarily indicative of future share price performance. (4) We determined non-GAAP net income to be the most important financial performance measure used to link Company performance to compensation actually paid to our PEO and non-PEO NEOs in 2023. This financial performance measure may not have been the most important financial performance measure for certain prior years shown and we may determine a different financial performance measure to be the most important financial performance measure in future years. See Appendix B for information regarding this non-GAAP financial measure. | |||
| Company Selected Measure Name | Non-GAAP Net Income | |||
| Named Executive Officers, Footnote | (1) Richard F. Pops was our PEO for each year presented. The individuals comprising the non-PEO NEOs for each year presented are listed below. 2020 2021 2022 2023 James M. Frates Iain M. Brown Iain M. Brown Iain M. Brown David J. Gaffin James M. Frates David J. Gaffin David J. Gaffin Craig C. Hopkinson, M.D. David J. Gaffin Craig C. Hopkinson, M.D. Craig C. Hopkinson, M.D. Michael J. Landine Craig C. Hopkinson, M.D. Blair C. Jackson Blair C. Jackson Blair C. Jackson | |||
| Peer Group Issuers, Footnote | (3) The peer group TSR shown in this table utilizes the Nasdaq Biotechnology Index (also known as the IBB Index ), which we also utilize in the stock performance graph required by Item 201(e) of Regulation S-K included in our Annual Report. The comparison assumes $100 was invested in the Company and in the Nasdaq Biotechnology Index , respectively, for the period starting December 31, 2019 through the end of the year shown. Historical share price performance is not necessarily indicative of future share price performance. | |||
| PEO Total Compensation Amount | $ 9,442,066 | $ 10,314,172 | $ 8,846,588 | $ 8,041,702 |
| PEO Actually Paid Compensation Amount | $ 8,983,892 | 8,321,591 | 11,225,263 | 6,883,292 |
| Adjustment To PEO Compensation, Footnote | (2) For 2023, the amounts shown reflect the exclusion and inclusion of those certain amounts for the PEO and the non-PEO NEOs shown in the following tables. Equity values are calculated in accordance with ASC 718. Amounts shown in each of the Exclusion of Stock Awards and Option Awards columns are equal to the total amounts from the Stock Awards and Option Awards columns set forth in the Summary Compensation Table on page 112 of this proxy statement. See the section entitled “Pay Versus Performance” on page 130 of the proxy statement for the 2023 Annual Meeting for the adjustments made to determine compensation actually paid amounts for prior years. Year Summary Compensation Table Total for PEO Exclusion of Stock Awards and Option Awards for PEO Inclusion of Equity Values for PEO Compensation Actually Paid to PEO 2023 9,442,066 ( 6,831,832 ) 6,373,658 8,983,892 The amounts shown in the Inclusion of Equity Values column in each of the above tables are derived from the following amounts: Year Year-End Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year for PEO Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards for PEO Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards that Vested During Year for PEO Fair Value at Last Day of Prior Year of Equity Awards Forfeited During Year for PEO Total - Inclusion of Equity Values for PEO 2023 3,934,846 2,022,849 415,963 — 6,373,658 | |||
| Non-PEO NEO Average Total Compensation Amount | $ 4,033,464 | 4,155,421 | 2,942,671 | 2,882,616 |
| Non-PEO NEO Average Compensation Actually Paid Amount | $ 4,190,097 | 4,206,760 | 2,882,217 | 2,656,656 |
| Adjustment to Non-PEO NEO Compensation Footnote | (2) For 2023, the amounts shown reflect the exclusion and inclusion of those certain amounts for the PEO and the non-PEO NEOs shown in the following tables. Equity values are calculated in accordance with ASC 718. Amounts shown in each of the Exclusion of Stock Awards and Option Awards columns are equal to the total amounts from the Stock Awards and Option Awards columns set forth in the Summary Compensation Table on page 112 of this proxy statement. See the section entitled “Pay Versus Performance” on page 130 of the proxy statement for the 2023 Annual Meeting for the adjustments made to determine compensation actually paid amounts for prior years. Year Average Summary Compensation Table Total for Non-PEO NEOs Average Exclusion of Stock Awards and Option Awards for Non-PEO NEOs Average Inclusion of Equity Values for Non-PEO NEOs Average Compensation Actually Paid to Non-PEO NEOs 2023 4,033,464 ( 2,902,745 ) 3,059,378 4,190,097 Year Average Year-End Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year for Non-PEO NEOs Average Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards for Non-PEO NEOs Average Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards that Vested During Year for Non-PEO NEOs Average Fair Value at Last Day of Prior Year of Equity Awards Forfeited During Year for Non-PEO NEOs Total - Average Inclusion of Equity Values for Non-PEO NEOs 2023 2,453,179 437,482 168,717 — 3,059,378 | |||
| Compensation Actually Paid vs. Total Shareholder Return | ||||
| Compensation Actually Paid vs. Net Income | ||||
| Compensation Actually Paid vs. Company Selected Measure | ||||
| Tabular List, Table | The most important financial performance measures used to link compensation actually paid to our NEOs for 2023 to Company performance are set forth below. For further information regarding these performance metrics and their function in our executive compensation program, see our Compensation Discussion and Analysis beginning on page 82 of this proxy statement. Proprietary Product Net Sales Relative Total Shareholder Return Non-GAAP Net Income * Non-GAAP Net Income* as a Percentage of Total Revenue EBITDA* as a Percentage of Total Revenue * See Appendix B for information regarding this non-GAAP financial target. | |||
| Total Shareholder Return Amount | $ 138.19 | 128.09 | 114.02 | 97.79 |
| Peer Group Total Shareholder Return Amount | 118.87 | 113.65 | 126.45 | 126.42 |
| Net Income (Loss) | $ 355,800,000 | $ (158,300,000) | $ (48,200,000) | $ (110,900,000) |
| Company Selected Measure Amount | 243,700,000 | 57,900,000 | 129,100,000 | 68,600,000 |
| PEO Name | Richard F. Pops | Richard F. Pops | Richard F. Pops | Richard F. Pops |
| Measure:: 1 | ||||
| Pay vs Performance Disclosure | ||||
| Name | Proprietary Product Net Sales | |||
| Measure:: 2 | ||||
| Pay vs Performance Disclosure | ||||
| Name | Relative Total Shareholder Return | |||
| Measure:: 3 | ||||
| Pay vs Performance Disclosure | ||||
| Name | Non-GAAP Net Income | |||
| Non-GAAP Measure Description | (4) We determined non-GAAP net income to be the most important financial performance measure used to link Company performance to compensation actually paid to our PEO and non-PEO NEOs in 2023. This financial performance measure may not have been the most important financial performance measure for certain prior years shown and we may determine a different financial performance measure to be the most important financial performance measure in future years. See Appendix B for information regarding this non-GAAP financial measure. | |||
| Measure:: 4 | ||||
| Pay vs Performance Disclosure | ||||
| Name | Non-GAAP Net Income* as a Percentage of Total Revenue | |||
| Measure:: 5 | ||||
| Pay vs Performance Disclosure | ||||
| Name | EBITDA* as a Percentage of Total Revenue | |||
| PEO | Exclusion of Stock Awards and Option Awards [Member] | ||||
| Pay vs Performance Disclosure | ||||
| Adjustment to Compensation, Amount | $ (6,831,832) | |||
| PEO | Yearend Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year [Member] | ||||
| Pay vs Performance Disclosure | ||||
| Adjustment to Compensation, Amount | 3,934,846 | |||
| PEO | Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards [Member] | ||||
| Pay vs Performance Disclosure | ||||
| Adjustment to Compensation, Amount | 2,022,849 | |||
| PEO | Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards that Vested During Year [Member] | ||||
| Pay vs Performance Disclosure | ||||
| Adjustment to Compensation, Amount | 415,963 | |||
| PEO | Inclusion of Equity Values [Member] | ||||
| Pay vs Performance Disclosure | ||||
| Adjustment to Compensation, Amount | 6,373,658 | |||
| Non-PEO NEO | Exclusion of Stock Awards and Option Awards [Member] | ||||
| Pay vs Performance Disclosure | ||||
| Adjustment to Compensation, Amount | (2,902,745) | |||
| Non-PEO NEO | Yearend Fair Value of Equity Awards Granted During Year That Remained Unvested as of Last Day of Year [Member] | ||||
| Pay vs Performance Disclosure | ||||
| Adjustment to Compensation, Amount | 2,453,179 | |||
| Non-PEO NEO | Change in Fair Value from Last Day of Prior Year to Last Day of Year of Unvested Equity Awards [Member] | ||||
| Pay vs Performance Disclosure | ||||
| Adjustment to Compensation, Amount | 437,482 | |||
| Non-PEO NEO | Change in Fair Value from Last Day of Prior Year to Vesting Date of Unvested Equity Awards that Vested During Year [Member] | ||||
| Pay vs Performance Disclosure | ||||
| Adjustment to Compensation, Amount | 168,717 | |||
| Non-PEO NEO | Inclusion of Equity Values [Member] | ||||
| Pay vs Performance Disclosure | ||||
| Adjustment to Compensation, Amount | $ 3,059,378 | |||
