Subsequent Event	9 Months Ended
Sep. 30, 2012
Subsequent Event [Abstract]
Subsequent Event	(13) Subsequent Event On November 9, 2012, the Company raised approximately $7.0 million in gross proceeds from a private financing with Pillar Pharmaceuticals II L.P., an investment partnership managed by one of the directors of the Company and one of the limited partners of Pillar. In the financing, the Company sold 424,242 shares of its Series E convertible preferred stock, par value $0.01 per share, (“Series E preferred stock”) and warrants to purchase up to 8,484,840 shares of its common stock, $0.001 par value per share, (the “warrants”). The initial conversion price of the Series E preferred stock and the initial exercise price of the warrants are $0.70 per share. The Company has agreed to pay to the holders of the Series E preferred stock quarterly dividends payable in cash in arrears at the rate of 4.6% per annum with the first dividend payment being due on March 31, 2013. Under the terms of the Series D preferred stock, any dividends paid to the holders of Series E preferred stock will also be paid to the holders of the Series D preferred stock on an as-converted to common stock basis. The Company has proposed an amendment to the Certificate of Designations of the Series D preferred stock to, among other things, modify the terms of the Series D preferred stock that require additional dividends. If such amendment is approved by the Company’s stockholders, the holders of the Series E preferred stock will become entitled to receive dividends payable in cash quarterly in arrears at the rate of 8% per annum and the holders of the Series D preferred stock would cease to be entitled to corresponding dividends. The net proceeds to Idera, excluding the proceeds of any exercise of the warrants, are expected to total approximately $6.2 million. The Company intends to use these funds for research and clinical development activities, the manufacturing of its product candidates, working capital and general corporate purposes, including the analysis of the data from the Company’s ongoing Phase 2 trial of IMO-3100, the conduct of a Phase 1 trial of IMO-8400 and the preparation for the further advancement of the Company’s autoimmune disease program in at least two indications. The securities offered by Idera in the private placement were not registered under the Securities Act of 1933, as amended, and cannot be offered or sold in the United States absent registration or an applicable exemption from registration requirements. The Company has agreed to file a registration statement with the Securities and Exchange Commission registering the resale of the shares of common stock issuable upon conversion of the Series E preferred stock and the shares of common stock issuable upon exercise of the warrants issued in the private placement.

Subsequent Event

9 Months Ended

Sep. 30, 2012

(13) Subsequent Event

On November 9, 2012, the Company raised approximately $7.0 million in gross proceeds from a private financing with Pillar Pharmaceuticals II L.P., an investment partnership managed by one of the directors of the Company and one of the limited partners of Pillar. In the financing, the Company sold 424,242 shares of its Series E convertible preferred stock, par value $0.01 per share, (“Series E preferred stock”) and warrants to purchase up to 8,484,840 shares of its common stock, $0.001 par value per share, (the “warrants”). The initial conversion price of the Series E preferred stock and the initial exercise price of the warrants are $0.70 per share. The Company has agreed to pay to the holders of the Series E preferred stock quarterly dividends payable in cash in arrears at the rate of 4.6% per annum with the first dividend payment being due on March 31, 2013. Under the terms of the Series D preferred stock, any dividends paid to the holders of Series E preferred stock will also be paid to the holders of the Series D preferred stock on an as-converted to common stock basis. The Company has proposed an amendment to the Certificate of Designations of the Series D preferred stock to, among other things, modify the terms of the Series D preferred stock that require additional dividends. If such amendment is approved by the Company’s stockholders, the holders of the Series E preferred stock will become entitled to receive dividends payable in cash quarterly in arrears at the rate of 8% per annum and the holders of the Series D preferred stock would cease to be entitled to corresponding dividends.

The net proceeds to Idera, excluding the proceeds of any exercise of the warrants, are expected to total approximately $6.2 million. The Company intends to use these funds for research and clinical development activities, the manufacturing of its product candidates, working capital and general corporate purposes, including the analysis of the data from the Company’s ongoing Phase 2 trial of IMO-3100, the conduct of a Phase 1 trial of IMO-8400 and the preparation for the further advancement of the Company’s autoimmune disease program in at least two indications.

The securities offered by Idera in the private placement were not registered under the Securities Act of 1933, as amended, and cannot be offered or sold in the United States absent registration or an applicable exemption from registration requirements. The Company has agreed to file a registration statement with the Securities and Exchange Commission registering the resale of the shares of common stock issuable upon conversion of the Series E preferred stock and the shares of common stock issuable upon exercise of the warrants issued in the private placement.