| Cover | Dec. 11, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Dec. 11, 2020 |
| Entity File Number | 001-31918 |
| Entity Registrant Name | Idera Pharmaceuticals, Inc. |
| Entity Central Index Key | 0000861838 |
| Entity Tax Identification Number | 04-3072298 |
| Entity Incorporation, State or Country Code | DE |
| Entity Address, Address Line One | 505 Eagleview Blvd. |
| Entity Address, Address Line Two | Suite 212 |
| Entity Address, City or Town | Exton |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 19341 |
| City Area Code | 484 |
| Local Phone Number | 348-1600 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.001 per share |
| Trading Symbol | IDRA |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
