| Cover - USD ($) | 12 Months Ended | ||
| Dec. 31, 2023 | Apr. 18, 2024 | Jun. 30, 2023 | |
| Cover [Abstract] | |||
| Document Type | 10-K/A | ||
| Amendment Flag | false | ||
| Document Annual Report | true | ||
| Document Transition Report | false | ||
| Document Period End Date | Dec. 31, 2023 | ||
| Document Fiscal Period Focus | FY | ||
| Document Fiscal Year Focus | 2023 | ||
| Current Fiscal Year End Date | --12-31 | ||
| Entity File Number | 001-36435 | ||
| Entity Registrant Name | Enzon Pharmaceuticals, Inc. | ||
| Entity Central Index Key | 0000727510 | ||
| Entity Tax Identification Number | 22-2372868 | ||
| Entity Incorporation, State or Country Code | DE | ||
| Entity Address, Address Line One | 20 Commerce Drive (Suite 135) | ||
| Entity Address, City or Town | Cranford | ||
| Entity Address, State or Province | NJ | ||
| Entity Address, Postal Zip Code | 07016 | ||
| City Area Code | 732 | ||
| Local Phone Number | 980-4500 | ||
| Trading Symbol | ENZN | ||
| Title of 12(g) Security | Common Stock, $0.01 par value | ||
| Entity Well-known Seasoned Issuer | No | ||
| Entity Voluntary Filers | No | ||
| Entity Current Reporting Status | Yes | ||
| Entity Interactive Data Current | Yes | ||
| Entity Filer Category | Non-accelerated Filer | ||
| Entity Small Business | true | ||
| Entity Emerging Growth Company | false | ||
| Entity Shell Company | false | ||
| Entity Public Float | $ 7,591,503 | ||
| Entity Common Stock, Shares Outstanding | 74,214,603 | ||
| ICFR Auditor Attestation Flag | false | ||
| Document Financial Statement Error Correction [Flag] | false | ||
| Auditor Name | EisnerAmper LLP | ||
| Auditor Firm ID | 274 | ||
| Auditor Location | Philadelphia, Pennsylvania |
