Legal Proceedings, Commitments and Contingencies	3 Months Ended
Mar. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Legal Proceedings, Commitments and Contingencies	Legal Proceedings, Commitments and Contingencies Legal Proceedings From time to time, the Company is subject to various pending or threatened legal actions and proceedings, including those that arise in the ordinary course of its business, which may include employment matters, breach of contract disputes and stockholder litigation. Such actions and proceedings are subject to many uncertainties and to outcomes that are not predictable with assurance and that may not be known for extended periods of time. The Company records a liability in its condensed consolidated financial statements for costs related to claims, including future legal costs, settlements and judgments, when the Company has assessed that a loss is probable and an amount can be reasonably estimated. If the reasonable estimate of a probable loss is a range, the Company records the most probable estimate of the loss or the minimum amount when no amount within the range is a better estimate than any other amount. The Company discloses a contingent liability even if the liability is not probable or the amount is not estimable, or both, if there is a reasonable possibility that a material loss may have been incurred. In the opinion of management, as of the date hereof, the amount of liability, if any, with respect to these matters, individually or in the aggregate, will not materially affect the Company’s consolidated results of operations, financial position or cash flows. The Company’s predecessor company, Galena, was involved in multiple legal proceedings and administrative actions, including stockholder class actions, both state and federal, some of which are ongoing and to which the Company is now subject as a result of the Merger. They are as follows: On February 13, 2017, a putative stockholder securities class action complaint was filed in the U.S. District Court for the District of New Jersey captioned, Miller v. Galena Biopharma, Inc., et al. On February 15, 2017, a putative stockholder securities class action complaint was filed in the U.S. District Court for the District of New Jersey entitled, Kattuah v. Galena Biopharma, Inc., et al. The actions assert that the defendants failed to disclose that Galena’s promotional practices for Abstral^® (fentanyl sublingual tablets) were allegedly improper and that Galena may be subject to civil and criminal liability, and that these alleged failures rendered Galena’s statements about its business misleading. Two groups of stockholders and one individual stockholder filed three motions to be appointed lead plaintiff on April 14, 2017 and April 17, 2017. Subsequently, one of the stockholders groups withdrew its motion for lead plaintiff status and the individual stockholder notified the Court that he did not object to the appointment of the remaining stockholder group, GALE investor group, as lead plaintiff. On July 17, 2017, the Court approved the GALE investor group as named lead plaintiff and its counsel as lead and liaison counsel. The Court also consolidated both actions. An amended complaint was filed on October 6, 2017. On December 15, 2017, Galena and the former officers and employees filed a motion to dismiss the amended complaint. The plaintiffs responded to a former officer’s motion to dismiss on February 13, 2018 and responded to Galena's and the other former officers' and employees' motion to dismiss in March 2018. The Company, as successor to Galena, and the former officers and employees filed a reply in April 2018. The Court will take the matter under advisement. It is not known when the Court will issue a ruling in this matter. On March 16, 2017, a complaint entitled Keller v. Ashton et al., CA No. 2:17-cv-01777 was filed in the U.S. District Court for the District of New Jersey against the Company’s then-existing directors and the Company, as a nominal defendant. The complaint purports to assert derivative claims for breach of fiduciary duty on the Company’s behalf against its directors based on substantially similar facts as alleged in the putative shareholder securities class action complaints mentioned above. The Company’s response to the complaint was due on June 1, 2017; however, on May 21, 2017, the Court entered a stay of the proceedings pending resolution of motions to dismiss in the securities litigations described above. On April 27, 2017, a putative stockholder class action was filed in the Court of Chancery of the State of Delaware captioned Patel vs. Galena Biopharma, Inc. et. al, CA No. 2017-0325-JTL seeking relief under Section 225 of the Delaware General Corporation Law (DGCL) and alleging breaches of fiduciary duties by Galena’s former board of directors and former interim chief executive officer regarding proposals to amend Galena’s certificate of incorporation to increase the amount of authorized shares of common stock and effectuate a reverse stock split at the July 2016 and October 2016 stockholder meetings, respectively. On June 2, 2017, an amended verified complaint was filed along with a motion to expedite the proceedings. On June 5, 2017, Galena filed a verified petition under Section 205 of the DGCL and a motion to expedite the proceedings. On June 8, 2017, the Court denied a request by the plaintiff to schedule a preliminary injunction motion and ordered a prompt trial on both the plaintiff and Galena’s claims. On June 20, 2017, the Court consolidated the claims into In re Galena Biopharma, Inc., C. A. No. 2017-0423-JTL. On July 10, 2017, the Court ordered that the trial of the claims be held on August 28, 30 and 31, 2017. On July 24, 2017, Galena entered into a binding settlement term sheet, which the Court enforced on November 30, 2017, over the objection of the plaintiff. On December 8, 2017, the Court set the hearing on the settlement for March 15, 2018. On December 11, 2017, the Court also granted an order validating the ratification votes at the special stockholder meeting held on July 6, 2017 and the certificate of amendments filed by Galena for the increase in authorized shares in 2011, 2013, 2015, and 2016 as well as for the reverse stock split in 2016. On February 22, 2018, the plaintiff filed his brief in support of the settlement as well as his request for attorneys’ fees and an incentive award. On March 1, 2018, the former directors and former interim chief executive officer responded to plaintiff’s brief. On February 28, 2018, the former directors and former interim chief executive officer requested the Court continue the date of the hearing to approve the settlement as the Company was working with the staff of the SEC to obtain the no-action letter required by the binding settlement term sheet. The Plaintiff objected to such continuance. On March 15, 2018, the Court ruled in favor of the Company and continued the settlement hearing for 90 days. Under the terms of the settlement, the class will receive a settlement payment of $1.3 million, in addition to attorney fees in an amount to be approved by the Court. The settlement payment of $1.3 million consists of $50,000 in cash to be paid by the Company or its insurers and $1,250,000 in unrestricted shares of the Company’s common stock (“Settlement Stock”), which valuation will be based on the volume-weighted average closing price for the 20 trading days immediately preceding the day before the transfer of the Settlement Stock to the settlement fund pursuant to the terms and conditions of the settlement. The Company anticipates that the Settlement Stock will be issued, pursuant to the terms of the Stipulation of Settlement, in a transaction that is exempt from the registration requirements of the Securities Act of 1933, as amended (the “Securities Act”), pursuant to Section 3(a)(10) of the Securities Act. Any amounts awarded by the Court for attorneys’ fees will be paid in part by the settlement fund and in part by the Company’s insurance carriers. Upon the effectiveness of the proposed settlement, the individual defendants will be released from the claims that were asserted or could have been asserted in the class action by class members participating in the settlement. On January 23, 2018, a complaint captioned Johnson v Schwartz et al., CA No. 2:18-cv-00903 was filed in the U.S. District Court for the District of New Jersey against Galena’s former directors, officers and employees and the Company as a nominal defendant. The complaint purports to assert derivative claims for breach of fiduciary duty on Galena’s behalf against its former directors, officers and employees based on substantially similar facts as alleged in the putative stockholder securities class action complaints and derivative complaints mentioned above, as well as making demand futility allegations against the current board of directors, who are not named as defendants. It is expected that the Company and the individual defendants will respond to the complaint through an appropriate pleading or motion and, if necessary, seek an order from the Court staying the proceedings pending further developments in the securities litigations described above. On or about April 9, 2018, JGB filed a lawsuit in the U.S. District Court for the Southern District of New York captioned JGB (Cayman) Newton, Ltd. v. Sellas Life Sciences Group, Inc., et al., Case 1:18-cv-3095 (DLC), or the JGB Action. The complaint in the JGB Action asserts claims under state law and federal securities law against the Company, the Company's Chief Executive Officer, Angelos M. Stergiou, M.D., ScD H.C, and the its Interim Chief Financial Officer, Aleksey N. Krylov (Mr. Krylov together with the Company and Dr. Stergiou, the Defendants). The complaint in the JGB Action alleges, among other things, that the Company breached a contractual obligation to deliver certain shares of its common stock to JGB and that, in the course of negotiations related to the Senior Secured Debenture agreement, the Defendants failed to disclose to JGB certain information regarding positive clinical trial results that was not then public. On or about May 2, 2018, JGB filed an amended complaint, adding as defendants Jane Wasman, Stephen Ghiglieri, David Scheinberg, M.D., Robert Van Nostrand and John Varian, each of whom is a member of the Company’s Board of Directors (the “Director Defendants”). The amended complaint, in addition to the allegations in the original complaint, alleges, among other things, that the Director Defendants are liable as “control persons” for the purposes of the purported securities laws violations committed by the Company, Dr. Stergiou and Mr. Krylov. According to the amended complaint, JGB seeks to receive an unspecified number of shares of the Company's common stock, a declaratory judgment in respect of the dispute underlying the litigation, damages, and costs and expenses incurred in the JGB action, among other things. The Company disputes the claims in the JGB Action and intends to defend against them vigorously.

Legal Proceedings, Commitments and Contingencies

Legal Proceedings

From time to time, the Company is subject to various pending or threatened legal actions and proceedings, including those that arise in the ordinary course of its business, which may include employment matters, breach of contract disputes and stockholder litigation. Such actions and proceedings are subject to many uncertainties and to outcomes that are not predictable with assurance and that may not be known for extended periods of time. The Company records a liability in its condensed consolidated financial statements for costs related to claims, including future legal costs, settlements and judgments, when the Company has assessed that a loss is probable and an amount can be reasonably estimated. If the reasonable estimate of a probable loss is a range, the Company records the most probable estimate of the loss or the minimum amount when no amount within the range is a better estimate than any other amount. The Company discloses a contingent liability even if the liability is not probable or the amount is not estimable, or both, if there is a reasonable possibility that a material loss may have been incurred. In the opinion of management, as of the date hereof, the amount of liability, if any, with respect to these matters, individually or in the aggregate, will not materially affect the Company’s consolidated results of operations, financial position or cash flows.

The Company’s predecessor company, Galena, was involved in multiple legal proceedings and administrative actions, including stockholder class actions, both state and federal, some of which are ongoing and to which the Company is now subject as a result of the Merger. They are as follows:

On February 13, 2017, a putative stockholder securities class action complaint was filed in the U.S. District Court for the District of New Jersey captioned, Miller v. Galena Biopharma, Inc., et al. On February 15, 2017, a putative stockholder securities class action complaint was filed in the U.S. District Court for the District of New Jersey entitled, Kattuah v. Galena Biopharma, Inc., et al. The actions assert that the defendants failed to disclose that Galena’s promotional practices for Abstral^® (fentanyl sublingual tablets) were allegedly improper and that Galena may be subject to civil and criminal liability, and that these alleged failures rendered Galena’s statements about its business misleading. Two groups of stockholders and one individual stockholder filed three motions to be appointed lead plaintiff on April 14, 2017 and April 17, 2017.

Subsequently, one of the stockholders groups withdrew its motion for lead plaintiff status and the individual stockholder notified the Court that he did not object to the appointment of the remaining stockholder group, GALE investor group, as lead plaintiff. On July 17, 2017, the Court approved the GALE investor group as named lead plaintiff and its counsel as lead and liaison counsel. The Court also consolidated both actions. An amended complaint was filed on October 6, 2017. On December 15, 2017, Galena and the former officers and employees filed a motion to dismiss the amended complaint. The plaintiffs responded to a former officer’s motion to dismiss on February 13, 2018 and responded to Galena's and the other former officers' and employees' motion to dismiss in March 2018. The Company, as successor to Galena, and the former officers and employees filed a reply in April 2018. The Court will take the matter under advisement. It is not known when the Court will issue a ruling in this matter.

On March 16, 2017, a complaint entitled Keller v. Ashton et al., CA No. 2:17-cv-01777 was filed in the U.S. District Court for the District of New Jersey against the Company’s then-existing directors and the Company, as a nominal defendant. The complaint purports to assert derivative claims for breach of fiduciary duty on the Company’s behalf against its directors based on substantially similar facts as alleged in the putative shareholder securities class action complaints mentioned above. The Company’s response to the complaint was due on June 1, 2017; however, on May 21, 2017, the Court entered a stay of the proceedings pending resolution of motions to dismiss in the securities litigations described above.

On April 27, 2017, a putative stockholder class action was filed in the Court of Chancery of the State of Delaware captioned Patel vs. Galena Biopharma, Inc. et. al, CA No. 2017-0325-JTL seeking relief under Section 225 of the Delaware General Corporation Law (DGCL) and alleging breaches of fiduciary duties by Galena’s former board of directors and former interim chief executive officer regarding proposals to amend Galena’s certificate of incorporation to increase the amount of authorized shares of common stock and effectuate a reverse stock split at the July 2016 and October 2016 stockholder meetings, respectively. On June 2, 2017, an amended verified complaint was filed along with a motion to expedite the proceedings. On June 5, 2017, Galena filed a verified petition under Section 205 of the DGCL and a motion to expedite the proceedings. On June 8, 2017, the Court denied a request by the plaintiff to schedule a preliminary injunction motion and ordered a prompt trial on both the plaintiff and Galena’s claims. On June 20, 2017, the Court consolidated the claims into In re Galena Biopharma, Inc., C. A. No. 2017-0423-JTL. On July 10, 2017, the Court ordered that the trial of the claims be held on August 28, 30 and 31, 2017. On July 24, 2017, Galena entered into a binding settlement term sheet, which the Court enforced on November 30, 2017, over the objection of the plaintiff. On December 8, 2017, the Court set the hearing on the settlement for March 15, 2018. On December 11, 2017, the Court also granted an order validating the ratification votes at the special stockholder meeting held on July 6, 2017 and the certificate of amendments filed by Galena for the increase in authorized shares in 2011, 2013, 2015, and 2016 as well as for the reverse stock split in 2016. On February 22, 2018, the plaintiff filed his brief in support of the settlement as well as his request for attorneys’ fees and an incentive award. On March 1, 2018, the former directors and former interim chief executive officer responded to plaintiff’s brief. On February 28, 2018, the former directors and former interim chief executive officer requested the Court continue the date of the hearing to approve the settlement as the Company was working with the staff of the SEC to obtain the no-action letter required by the binding settlement term sheet. The Plaintiff objected to such continuance. On March 15, 2018, the Court ruled in favor of the Company and continued the settlement hearing for 90 days.

Under the terms of the settlement, the class will receive a settlement payment of $1.3 million, in addition to attorney fees in an amount to be approved by the Court. The settlement payment of $1.3 million consists of $50,000 in cash to be paid by the Company or its insurers and $1,250,000 in unrestricted shares of the Company’s common stock (“Settlement Stock”), which valuation will be based on the volume-weighted average closing price for the 20 trading days immediately preceding the day before the transfer of the Settlement Stock to the settlement fund pursuant to the terms and conditions of the settlement. The Company anticipates that the Settlement Stock will be issued, pursuant to the terms of the Stipulation of Settlement, in a transaction that is exempt from the registration requirements of the Securities Act of 1933, as amended (the “Securities Act”), pursuant to Section 3(a)(10) of the Securities Act. Any amounts awarded by the Court for attorneys’ fees will be paid in part by the settlement fund and in part by the Company’s insurance carriers. Upon the effectiveness of the proposed settlement, the individual defendants will be released from the claims that were asserted or could have been asserted in the class action by class members participating in the settlement.

On January 23, 2018, a complaint captioned Johnson v Schwartz et al., CA No. 2:18-cv-00903 was filed in the U.S. District Court for the District of New Jersey against Galena’s former directors, officers and employees and the Company as a nominal defendant. The complaint purports to assert derivative claims for breach of fiduciary duty on Galena’s behalf against its former directors, officers and employees based on substantially similar facts as alleged in the putative stockholder securities class action complaints and derivative complaints mentioned above, as well as making demand futility allegations against the current board of directors, who are not named as defendants. It is expected that the Company and the individual defendants will respond to the complaint through an appropriate pleading or motion and, if necessary, seek an order from the Court staying the proceedings pending further developments in the securities litigations described above.

On or about April 9, 2018, JGB filed a lawsuit in the U.S. District Court for the Southern District of New York captioned JGB (Cayman) Newton, Ltd. v. Sellas Life Sciences Group, Inc., et al., Case 1:18-cv-3095 (DLC), or the JGB Action. The complaint in the JGB Action asserts claims under state law and federal securities law against the Company, the Company's Chief Executive Officer, Angelos M. Stergiou, M.D., ScD H.C, and the its Interim Chief Financial Officer, Aleksey N. Krylov (Mr. Krylov together with the Company and Dr. Stergiou, the Defendants). The complaint in the JGB Action alleges, among other things, that the Company breached a contractual obligation to deliver certain shares of its common stock to JGB and that, in the course of negotiations related to the Senior Secured Debenture agreement, the Defendants failed to disclose to JGB certain information regarding positive clinical trial results that was not then public. On or about May 2, 2018, JGB filed an amended complaint, adding as defendants Jane Wasman, Stephen Ghiglieri, David Scheinberg, M.D., Robert Van Nostrand and John Varian, each of whom is a member of the Company’s Board of Directors (the “Director Defendants”). The amended complaint, in addition to the allegations in the original complaint, alleges, among other things, that the Director Defendants are liable as “control persons” for the purposes of the purported securities laws violations committed by the Company, Dr. Stergiou and Mr. Krylov. According to the amended complaint, JGB seeks to receive an unspecified number of shares of the Company's common stock, a declaratory judgment in respect of the dispute underlying the litigation, damages, and costs and expenses incurred in the JGB action, among other things. The Company disputes the claims in the JGB Action and intends to defend against them vigorously.