| Cover Page | 12 Months Ended |
| Dec. 31, 2022 | |
| Cover [Abstract] | |
| Document Type | DEF 14A |
| Entity Registrant Name | Agenus Inc. |
| Amendment Flag | false |
| Entity Central Index Key | 0001098972 |
| Pay vs Performance Disclosure - USD ($) | 12 Months Ended | |||
| Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | ||
| Pay vs Performance Disclosure [Table] | ||||
| Pay vs Performance [Table Text Block] | Value of Initial Fixed $100 Investment Based On: Year Summary Compensation Table Total for PEO ($) (1) Compensation Actually Paid to PEO ($) (2) Average Summary Compensation Table Total for Non-PEO NEOs ($) (3) Average Compensation Actually Paid to Non-PEO NEOs ($) (4) Total Shareholder Return (5) Peer Group Total Shareholder Return (6) Net Loss ($) (7) Company Selected Measure 2022 5,626,310 ( 1,356,412 ) 969,686 1,088,774 ( 0.25 ) ( 0.11 ) ( 230,655,670 ) N/A 2021 9,757,448 8,844,707 2,809,564 2,505,512 0.01 ( 0.01 ) ( 28,723,733 ) N/A 2020 5,637,244 ( 1,572,801 ) 1,178,911 755,519 ( 0.22 ) 0.26 ( 182,891,108 ) N/A (1) Represents the total from the Summary Compensation Table in each applicable year for Dr. Armen , who was the PEO for all three years reported in the table (2020-2022). (2) Represents the amount of compensation actually paid to Dr. Armen, as computed in accordance with Item 402(v) of Regulation S-K. The chart below details the adjustments made to the PEO’s total compensation for each year to determine the compensation actually paid for the relevant year. (3) Represents the average total from the Summary Compensation Table in each applicable year for the Non-PEO NEOs, which are comprised of: for 2022, Dr. O’Day and Ms. Klaskin; for 2021, Drs. Buell and O’Day, Ms. Klaskin, and Mr. Krauss; and for 2020, Dr. Buell, Mr. Kearns, Ms. Klaskin, and Mr. Krauss. (4) Represents the average amount of compensation actually paid to the Non-PEO NEOs, as computed in accordance with Item 402(v) of Regulation S-K. The chart below details the adjustments made to the total compensation for each year to determine the compensation actually paid for the relevant year. (5) Represents the cumulative total return on $100 invested in the Company’s common stock as of the last day of public trading of the Company’s common stock in fiscal year 2019 through the last day of public trading of the Company’s common stock in the applicable fiscal year for which the cumulative total return is reported. The Company did not pay dividends for any of 2022, 2021 or 2020. (6) Represents the weighted cumulative total return on $100 invested as of the last day of public trading in fiscal year 2019 through the last day of public trading in the applicable fiscal year for which the cumulative total return is reported. The peer group used for this purpose is the Nasdaq Biotechnology Index for all three years disclosed, which is the same peer group used in our Annual Report on Form 10-K for each of these years for purposes of Item 201(e) of Regulation S-K. The return of this index is calculated assuming reinvestment of dividends during the period presented. (7) Represents net income (loss) disclosed in our Annual Report on Form 10-K for the years ended December 31, 2022, 2021 and 2020, as applicable. | |||
| Named Executive Officers, Footnote [Text Block] | (1) Represents the total from the Summary Compensation Table in each applicable year for Dr. Armen , who was the PEO for all three years reported in the table (2020-2022). (2) Represents the amount of compensation actually paid to Dr. Armen, as computed in accordance with Item 402(v) of Regulation S-K. The chart below details the adjustments made to the PEO’s total compensation for each year to determine the compensation actually paid for the relevant year. | |||
| Peer Group Issuers, Footnote [Text Block] | (6) Represents the weighted cumulative total return on $100 invested as of the last day of public trading in fiscal year 2019 through the last day of public trading in the applicable fiscal year for which the cumulative total return is reported. The peer group used for this purpose is the Nasdaq Biotechnology Index for all three years disclosed, which is the same peer group used in our Annual Report on Form 10-K for each of these years for purposes of Item 201(e) of Regulation S-K. The return of this index is calculated assuming reinvestment of dividends during the period presented. | |||
| PEO Total Compensation Amount | [1] | $ 5,626,310 | $ 9,757,448 | $ 5,637,244 |
| PEO Actually Paid Compensation Amount | [2] | $ (1,356,412) | 8,844,707 | (1,572,801) |
| Adjustment To PEO Compensation, Footnote [Text Block] | Compensation Actually Paid Adjustments Year Summary Compensation Table Total ($) (Minus) Grant Date Fair Value of Stock Option and Stock Awards Granted in Fiscal Year ($) Plus Fair Value at Fiscal Year-End of Outstanding and Unvested Stock Option and Stock Awards Granted in Fiscal Year ($) Plus (Minus) Change in Fair Value of Outstanding and Unvested Stock Option and Stock Grant Awards Granted in Prior Fiscal Years ($) Fair Value as of the Vesting Date of Awards Granted and Vest in the Same Year ($) Plus (Minus) Change in Fair Value as of Vesting Date of Stock Option and Stock Awards Granted in Prior Fiscal Years for which Applicable Vesting Conditions were satisfied during Fiscal Year ($) (Minus) Fair Value as of Prior Fiscal Year-End of Stock Option and Stock Awards Granted in Prior Fiscal Years that Failed to Meet applicable Vesting conditions during Fiscal Year ($) Compensation Actually Paid ($) PEO 2022 5,626,310 ( 3,999,800 ) 2,887,244 ( 1,600,793 ) 937,498 ( 2,359,064 ) ( 2,847,806 ) ( 1,356,412 ) 2021 9,757,448 ( 8,276,866 ) 3,981,765 ( 168,188 ) 589,498 2,961,050 - 8,844,707 2020 5,637,244 ( 4,563,132 ) 3,634,486 ( 3,083,658 ) - ( 10,353 ) ( 3,187,388 ) ( 1,572,801 ) Non-PEO NEOs (Average) 2022 969,686 ( 261,250 ) 189,950 ( 27,408 ) 254,873 ( 14,653 ) ( 22,424 ) 1,088,774 2021 2,809,564 ( 1,423,324 ) 734,629 ( 12,412 ) 130,087 309,922 ( 42,954 ) 2,505,512 2020 1,178,911 ( 759,380 ) 624,484 ( 222,779 ) - ( 18,190 ) ( 47,527 ) 755,519 | |||
| Non-PEO NEO Average Total Compensation Amount | [3] | $ 969,686 | 2,809,564 | 1,178,911 |
| Non-PEO NEO Average Compensation Actually Paid Amount | [4] | $ 1,088,774 | 2,505,512 | 755,519 |
| Adjustment to Non-PEO NEO Compensation Footnote [Text Block] | Compensation Actually Paid Adjustments Year Summary Compensation Table Total ($) (Minus) Grant Date Fair Value of Stock Option and Stock Awards Granted in Fiscal Year ($) Plus Fair Value at Fiscal Year-End of Outstanding and Unvested Stock Option and Stock Awards Granted in Fiscal Year ($) Plus (Minus) Change in Fair Value of Outstanding and Unvested Stock Option and Stock Grant Awards Granted in Prior Fiscal Years ($) Fair Value as of the Vesting Date of Awards Granted and Vest in the Same Year ($) Plus (Minus) Change in Fair Value as of Vesting Date of Stock Option and Stock Awards Granted in Prior Fiscal Years for which Applicable Vesting Conditions were satisfied during Fiscal Year ($) (Minus) Fair Value as of Prior Fiscal Year-End of Stock Option and Stock Awards Granted in Prior Fiscal Years that Failed to Meet applicable Vesting conditions during Fiscal Year ($) Compensation Actually Paid ($) PEO 2022 5,626,310 ( 3,999,800 ) 2,887,244 ( 1,600,793 ) 937,498 ( 2,359,064 ) ( 2,847,806 ) ( 1,356,412 ) 2021 9,757,448 ( 8,276,866 ) 3,981,765 ( 168,188 ) 589,498 2,961,050 - 8,844,707 2020 5,637,244 ( 4,563,132 ) 3,634,486 ( 3,083,658 ) - ( 10,353 ) ( 3,187,388 ) ( 1,572,801 ) Non-PEO NEOs (Average) 2022 969,686 ( 261,250 ) 189,950 ( 27,408 ) 254,873 ( 14,653 ) ( 22,424 ) 1,088,774 2021 2,809,564 ( 1,423,324 ) 734,629 ( 12,412 ) 130,087 309,922 ( 42,954 ) 2,505,512 2020 1,178,911 ( 759,380 ) 624,484 ( 222,779 ) - ( 18,190 ) ( 47,527 ) 755,519 | |||
| Equity Valuation Assumption Difference, Footnote [Text Block] | For the values of equity awards included in the above table, fair values are calculated in accordance with FASB ASC Topic 718 and, in the case of performance-based stock options and performance shares, are based on the probable outcome of the performance conditions as of the applicable measuring date (or actual performance results approved by our Compensation Committee as of the applicable vesting date). Otherwise, the valuation assumptions used to calculate fair values did not materially differ from those used in our disclosures of fair value as of the grant date. | |||
| Compensation Actually Paid vs. Total Shareholder Return [Text Block] | The following chart sets forth the relationship between CAP to our PEO, the average of CAP to our other Non-PEO NEOs, each as set forth in the table above, and our TSR over the three-year period from 2020 through 2022. | |||
| Total Shareholder Return Vs Peer Group [Text Block] | The following chart compares our TSR over the three-year period from 2020 through 2022 to that of the NASDAQ Biotechnology Index over the same time period. | |||
| Total Shareholder Return Amount | [5] | $ (0.25) | 0.01 | (0.22) |
| Peer Group Total Shareholder Return Amount | [6] | (0.11) | (0.01) | 0.26 |
| Net Income (Loss) | [7] | $ (230,655,670) | $ (28,723,733) | $ (182,891,108) |
| PEO Name | Dr. Armen | Dr. Armen | Dr. Armen | |
| Additional 402(v) Disclosure [Text Block] | As required by Item 402(v) of Regulation S-K, we are providing the following disclosure regarding the relationship between executive compensation actually paid and certain financial performance of the Company for Dr. Armen, our principal executive officer (“ PEO ”), and our named executive officers other than our PEO (“ Non-PEO NEOs ”) for the fiscal years listed below. Our Compensation Committee did not consider the pay versus performance disclosure below in making its pay decisions for any of the years shown. | |||
| PEO [Member] | Grant Date Fair Value Of Stock Option And Stock Awards Granted In Fiscal Year [Member] | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | $ (3,999,800) | $ (8,276,866) | $ (4,563,132) | |
| PEO [Member] | Fair Value at Fiscal Year-End of Outstanding and Unvested Stock Option and Stock Awards Granted in Fiscal Year [Member] | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | 2,887,244 | 3,981,765 | 3,634,486 | |
| PEO [Member] | Change in Fair Value of Outstanding and Unvested Stock Option and Stock Grant Awards Granted in Prior Fiscal Years [Member] | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | (1,600,793) | (168,188) | (3,083,658) | |
| PEO [Member] | Fair Value as of the Vesting Date of Awards Granted and Vest in the Same Year [Member] | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | 937,498 | 589,498 | ||
| PEO [Member] | Change in Fair Value as of Vesting Date of Stock Option and Stock Awards Granted in Prior Fiscal Years for which Applicable Vesting Conditions were satisfied during Fiscal Year [Member] | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | (2,359,064) | 2,961,050 | (10,353) | |
| PEO [Member] | Fair Value as of Prior Fiscal Year-End of Stock Option and Stock Awards Granted in Prior Fiscal Years that Failed to Meet applicable Vesting conditions during Fiscal Year [Member] | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | (2,847,806) | (3,187,388) | ||
| Non-PEO NEO [Member] | Grant Date Fair Value Of Stock Option And Stock Awards Granted In Fiscal Year [Member] | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | (261,250) | (1,423,324) | (759,380) | |
| Non-PEO NEO [Member] | Fair Value at Fiscal Year-End of Outstanding and Unvested Stock Option and Stock Awards Granted in Fiscal Year [Member] | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | 189,950 | 734,629 | 624,484 | |
| Non-PEO NEO [Member] | Change in Fair Value of Outstanding and Unvested Stock Option and Stock Grant Awards Granted in Prior Fiscal Years [Member] | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | (27,408) | (12,412) | (222,779) | |
| Non-PEO NEO [Member] | Fair Value as of the Vesting Date of Awards Granted and Vest in the Same Year [Member] | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | 254,873 | 130,087 | ||
| Non-PEO NEO [Member] | Change in Fair Value as of Vesting Date of Stock Option and Stock Awards Granted in Prior Fiscal Years for which Applicable Vesting Conditions were satisfied during Fiscal Year [Member] | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | (14,653) | 309,922 | (18,190) | |
| Non-PEO NEO [Member] | Fair Value as of Prior Fiscal Year-End of Stock Option and Stock Awards Granted in Prior Fiscal Years that Failed to Meet applicable Vesting conditions during Fiscal Year [Member] | ||||
| Pay vs Performance Disclosure [Table] | ||||
| Adjustment to Compensation Amount | $ (22,424) | $ (42,954) | $ (47,527) | |
| [1] Represents the total from the Summary Compensation Table in each applicable year for Dr. Armen , who was the PEO for all three years reported in the table (2020-2022). Represents the amount of compensation actually paid to Dr. Armen, as computed in accordance with Item 402(v) of Regulation S-K. The chart below details the adjustments made to the PEO’s total compensation for each year to determine the compensation actually paid for the relevant year. Represents the average total from the Summary Compensation Table in each applicable year for the Non-PEO NEOs, which are comprised of: for 2022, Dr. O’Day and Ms. Klaskin; for 2021, Drs. Buell and O’Day, Ms. Klaskin, and Mr. Krauss; and for 2020, Dr. Buell, Mr. Kearns, Ms. Klaskin, and Mr. Krauss. Represents the average amount of compensation actually paid to the Non-PEO NEOs, as computed in accordance with Item 402(v) of Regulation S-K. The chart below details the adjustments made to the total compensation for each year to determine the compensation actually paid for the relevant year. Represents the cumulative total return on $100 invested in the Company’s common stock as of the last day of public trading of the Company’s common stock in fiscal year 2019 through the last day of public trading of the Company’s common stock in the applicable fiscal year for which the cumulative total return is reported. The Company did not pay dividends for any of 2022, 2021 or 2020. Represents the weighted cumulative total return on $100 invested as of the last day of public trading in fiscal year 2019 through the last day of public trading in the applicable fiscal year for which the cumulative total return is reported. The peer group used for this purpose is the Nasdaq Biotechnology Index for all three years disclosed, which is the same peer group used in our Annual Report on Form 10-K for each of these years for purposes of Item 201(e) of Regulation S-K. The return of this index is calculated assuming reinvestment of dividends during the period presented. Represents net income (loss) disclosed in our Annual Report on Form 10-K for the years ended December 31, 2022, 2021 and 2020, as applicable. | ||||
