Legal Proceedings	12 Months Ended
Dec. 31, 2017
Legal Proceedings [Abstract]
Legal Proceedings	Note 9 - Legal Proceedings From time to time, the Company and its subsidiaries may be named as a defendant in various lawsuits or proceedings. At the current time except as set forth below, the Company is unaware of any legal proceedings pending against the Company. The Company intends to aggressively contest all litigation and contingencies, as well as pursue all sources for contributions to settlements. The Company is a party to material legal proceedings as follows: AmBase Corp., et al. v. 111 West 57^th Sponsor LLC, et al. In April 2016, AmBase initiated a litigation in the New York State Supreme Court for New York County (the "NY Court"), Index No. 652301/2016, ("AmBase v. 111 West 57^th Sponsor LLC, et al.") (the "111 West 57^th Action"). The defendants in that litigation were 111 West 57th Sponsor LLC, 111 West 57th JDS LLC, PMG West 57th Street LLC, 111 West 57th Control LLC, 111 West 57th Developer LLC, Elliot Joseph, 111 West 57^th KM Equity LLC, 111 West 57^th KM Group LLC, Kevin Maloney, Matthew Phillips, Michael Stern, Ned White and Franklin R. Kaiman (collectively, "Defendants") and nominal defendant 111 West 57th Partners LLC. AmBase alleges in that action, that Defendants violated multiple provisions in the JV Agreement, including by failing to honor the exercise of AmBase's contractual "equity put right" as set forth in the JV Agreement (the "Equity Put Right"). AmBase is seeking compensatory damages, as well as punitive damages, indemnification and equitable relief including a declaration of the parties' rights, and an accounting. The Company has also demanded from the Sponsor access to the books and records for the 111 West 57^th Property which the Sponsor refused, claiming they have provided all books and records as required. The Defendants filed motions to dismiss, and on January 12, 2018, the NY Court issued an opinion allowing some of AmBase's claims to go forward and dismissing others. Among other claims that the NY Court declined to dismiss was AmBase's claim that the Defendants violated the implied covenant of good faith and fair dealing by frustrating AmBase's Equity Put Right by declining to produce a timely budget. Claims that the NY Court dismissed included AmBase's claim that the Defendants breached their contract with AmBase by financing capital contributions for the project through funds obtained from third parties. On January 16, 2018, some of the Defendants wrote to the NY Court suggesting that the opinion contained certain clerical errors and was missing a page. On January 18, 2018, the NY Court removed its previous opinion from the docket and on January 29, 2018, posted a revised opinion. A discovery conference in this case is currently scheduled for February 27, 2018. For additional information with regard to the Company's investment in the 111 West 57^th Property, see Note 4. AmBase Corp., et al. v. Spruce Capital Partners, et al. In July 2017, the Company initiated a second litigation in the NY Court, Index No. 655031/2017, (the "111 West 57^th Spruce Action"). The defendants in the 111 West 57^th Spruce action are 111 W57 Mezz Investor, LLC, Spruce Capital Partners LLC, 111 West 57th Sponsor LLC, Michael Z. Stern, and Kevin P. Maloney (collectively, "Defendants") and nominal defendants 111 West 57th Partners LLC and 111 West 57^th Mezz 1 LLC. Spruce had given notice to the junior mezzanine borrower that it proposed to accept the pledged collateral (including the joint venture members' collective interest in the property) in full satisfaction of the joint venture's indebtedness under the Junior Mezzanine Loan (i.e., a "Strict Foreclosure"). After the Sponsors refused to object to Spruce's proposal on behalf of the junior mezzanine borrower, and Spruce refused to commit to honor Investment LLC's objection on its own behalf, the Company initiated this litigation to obtain injunctive relief halting the Strict Foreclosure. For additional information on the events leading to this litigation see Note 4. On July 26, 2017, the NY Court issued a temporary restraining order barring Spruce from accepting the collateral, pending a preliminary injunction hearing scheduled for August 14, 2017. Spruce and the Sponsors subsequently filed papers in opposition to the request for a preliminary injunction and cross-motions to dismiss and quash subpoenas. On August 14, 2017, the NY Court postponed the hearing until August 28, 2017, keeping the temporary restraining order preventing a Strict Foreclosure in effect until the August 28, 2017, hearing. Subsequently the Company filed response briefs in support of their request for injunctive relief halting the Strict Foreclosure process and briefs in opposition to the motions to quash the subpoenas. On August 28, 2017, the NY Court held a preliminary injunction hearing, lifted the temporary restraining order, denied Plaintiffs' request for a preliminary injunction, and granted Defendants' cross-motions. In order to prevent the Strict Foreclosure process from going forward, the Company immediately obtained an interim stay from the New York Supreme Court Appellate Division, First Judicial Department ("Appellate Division"). That stay remained in place until four (4) P.M. August 29, 2017, permitting the Company to obtain an appealable order, notice an appeal, and move for a longer-term stay or injunctive relief pending appeal. The Appellate Division held a hearing on August 29, 2017, to consider the Company's motion for an interim stay or injunctive relief pending appeal, both of which it denied, thus allowing the purported Strict Foreclosure to move forward. The Company will continue to challenge the validity of the actions that led to this purported transfer of title, including appeal. On August 30, 2017, Spruce issued a Notice of Retention of Pledged Collateral in Full Satisfaction of Indebtedness. By purporting to accept the pledged collateral, pursuant to a Strict Foreclosure process, Spruce claims to have completed the retention of the collateral pledged by the junior mezzanine borrower, and therefore, the Company's interest in the 111 West 57th Street Property. The carrying value of the Company's equity investment in the 111 West 57^th Property represented a substantial portion of the Company's assets and net equity value. The Company has an appeal pending on its challenge to the Strict Foreclosure, which has not yet been resolved. The Company is currently attempting to have the Appellate Division declare the Strict Foreclosure invalid and to enjoin the Strict Foreclosure. The Company moved for a stay or injunctive relief pending appeal, and that motion was denied by the appellate court on January 18, 2018. Since the Company is not party to the Loan Agreements, it does not have access to communications with the lenders, except for those individual communications the Sponsors have elected to share. The Company has continued to demand access to such information, including access to the books and records for the 111 West 57^th Property both under the JV Agreement and as part of the 111 West 57^th Action and the 111 West 57^th Spruce Action. For additional information with regard to the Company's recording of an impairment of its equity investment in the 111 West 57^th Property; see Note 4. The carrying value of the Company's equity investment in the 111 West 57^th Property represented substantially all of the Company's assets and net equity value. For information relating to the Litigation Funding Agreement entered into between the Company and Mr. Richard A. Bianco, the Company's President and Chief Executive Officer, see Note 10. With respect to its disputes and litigation relating to its interest in the 111 West 57th Property, the Company is continuing to pursue various legal courses of action, as well as considering other possible economic strategies, including the possible sale of the Company's interest in and/or rights with respect to the 111 West 57th Property. The Company is continuing to pursue other options to realize the Company's investment value and/or protect its legal rights. The Company can give no assurances regarding the outcome of the matters described herein, including as to the effect of Spruce's actions described herein, whether the Sponsors will perform their contractual commitments to the Company under the JV Agreement, as to what further action, if any, the lenders may take with respect to the project, as to the ultimate resolution of the ongoing litigation proceedings relating to the Company's investment interest in the 111 West 57^th Property, as to the ultimate effect of the Sponsors', the Company's or the lenders' actions on the project, as to the completion or ultimate success of the project, or as to the value or ultimate realization of any portion of the Company's equity investment in the 111 West 57^th Street Property. For additional information on the Company's investment in the 111 West 57^th Property and the Company's legal actions related thereto, see Note 9. While the Company's management is evaluating future courses of action to protect and/or recover the value of the Company's equity investment in the 111 West 57^th Property, the adverse developments make it uncertain as to whether any such courses of action will be successful. Any such efforts are likely to require sustained effort over a period of time, and require substantial additional financial resources. Inability to recover all or most of such value would in all likelihood have a material adverse effect on the Company's financial condition and future prospects. IsZo Capital L.P. derivatively and on behalf of AmBase Corporation v. Richard A. Bianco, et al. In February 2018, IsZo Capital L.P. commenced an action, IsZo Capital L.P. derivatively and on behalf of AmBase Corporation v. Richard A. Bianco, et al., Index No. 650812/2018 in the New York State Supreme Court for New York County (the "IsZo Capital L.P. action"). The defendants in the action include all officers and directors of AmBase Corporation and AmBase Corporation as a nominal defendant. The plaintiff alleges various breaches of fiduciary duty against all of the directors and officers concerning the decisions made in the 111 West 57^th Street Property investment and a certain litigation funding agreement. IsZo Capital L.P. also seeks declaratory judgment relief concerning a litigation funding agreement and the 111 West 57^th Street Property. AmBase and the officers and directors intend to vigorously defend themselves and will move to dismiss the Complaint when all of the officers and directors have been served with the Summons and Complaint. The Company can give no assurances regarding the outcome of the matters described herein.

Note 9 - Legal Proceedings

From time to time, the Company and its subsidiaries may be named as a defendant in various lawsuits or proceedings. At the current time except as set forth below, the Company is unaware of any legal proceedings pending against the Company. The Company intends to aggressively contest all litigation and contingencies, as well as pursue all sources for contributions to settlements.

The Company is a party to material legal proceedings as follows:

AmBase Corp., et al. v. 111 West 57^th Sponsor LLC, et al. In April 2016, AmBase initiated a litigation in the New York State Supreme Court for New York County (the "NY Court"), Index No. 652301/2016, ("AmBase v. 111 West 57^th Sponsor LLC, et al.") (the "111 West 57^th Action"). The defendants in that litigation were 111 West 57th Sponsor LLC, 111 West 57th JDS LLC, PMG West 57th Street LLC, 111 West 57th Control LLC, 111 West 57th Developer LLC, Elliot Joseph, 111 West 57^th KM Equity LLC, 111 West 57^th KM Group LLC, Kevin Maloney, Matthew Phillips, Michael Stern, Ned White and Franklin R. Kaiman (collectively, "Defendants") and nominal defendant 111 West 57th Partners LLC. AmBase alleges in that action, that Defendants violated multiple provisions in the JV Agreement, including by failing to honor the exercise of AmBase's contractual "equity put right" as set forth in the JV Agreement (the "Equity Put Right"). AmBase is seeking compensatory damages, as well as punitive damages, indemnification and equitable relief including a declaration of the parties' rights, and an accounting. The Company has also demanded from the Sponsor access to the books and records for the 111 West 57^th Property which the Sponsor refused, claiming they have provided all books and records as required. The Defendants filed motions to dismiss, and on January 12, 2018, the NY Court issued an opinion allowing some of AmBase's claims to go forward and dismissing others. Among other claims that the NY Court declined to dismiss was AmBase's claim that the Defendants violated the implied covenant of good faith and fair dealing by frustrating AmBase's Equity Put Right by declining to produce a timely budget. Claims that the NY Court dismissed included AmBase's claim that the Defendants breached their contract with AmBase by financing capital contributions for the project through funds obtained from third parties. On January 16, 2018, some of the Defendants wrote to the NY Court suggesting that the opinion contained certain clerical errors and was missing a page. On January 18, 2018, the NY Court removed its previous opinion from the docket and on January 29, 2018, posted a revised opinion. A discovery conference in this case is currently scheduled for February 27, 2018. For additional information with regard to the Company's investment in the 111 West 57^th Property, see Note 4.

AmBase Corp., et al. v. Spruce Capital Partners, et al. In July 2017, the Company initiated a second litigation in the NY Court, Index No. 655031/2017, (the "111 West 57^th Spruce Action"). The defendants in the 111 West 57^th Spruce action are 111 W57 Mezz Investor, LLC, Spruce Capital Partners LLC, 111 West 57th Sponsor LLC, Michael Z. Stern, and Kevin P. Maloney (collectively, "Defendants") and nominal defendants 111 West 57th Partners LLC and 111 West 57^th Mezz 1 LLC.

Spruce had given notice to the junior mezzanine borrower that it proposed to accept the pledged collateral (including the joint venture members' collective interest in the property) in full satisfaction of the joint venture's indebtedness under the Junior Mezzanine Loan (i.e., a "Strict Foreclosure"). After the Sponsors refused to object to Spruce's proposal on behalf of the junior mezzanine borrower, and Spruce refused to commit to honor Investment LLC's objection on its own behalf, the Company initiated this litigation to obtain injunctive relief halting the Strict Foreclosure. For additional information on the events leading to this litigation see Note 4.

On July 26, 2017, the NY Court issued a temporary restraining order barring Spruce from accepting the collateral, pending a preliminary injunction hearing scheduled for August 14, 2017. Spruce and the Sponsors subsequently filed papers in opposition to the request for a preliminary injunction and cross-motions to dismiss and quash subpoenas. On August 14, 2017, the NY Court postponed the hearing until August 28, 2017, keeping the temporary restraining order preventing a Strict Foreclosure in effect until the August 28, 2017, hearing. Subsequently the Company filed response briefs in support of their request for injunctive relief halting the Strict Foreclosure process and briefs in opposition to the motions to quash the subpoenas.

On August 28, 2017, the NY Court held a preliminary injunction hearing, lifted the temporary restraining order, denied Plaintiffs' request for a preliminary injunction, and granted Defendants' cross-motions. In order to prevent the Strict Foreclosure process from going forward, the Company immediately obtained an interim stay from the New York Supreme Court Appellate Division, First Judicial Department ("Appellate Division"). That stay remained in place until four (4) P.M. August 29, 2017, permitting the Company to obtain an appealable order, notice an appeal, and move for a longer-term stay or injunctive relief pending appeal. The Appellate Division held a hearing on August 29, 2017, to consider the Company's motion for an interim stay or injunctive relief pending appeal, both of which it denied, thus allowing the purported Strict Foreclosure to move forward. The Company will continue to challenge the validity of the actions that led to this purported transfer of title, including appeal.

On August 30, 2017, Spruce issued a Notice of Retention of Pledged Collateral in Full Satisfaction of Indebtedness. By purporting to accept the pledged collateral, pursuant to a Strict Foreclosure process, Spruce claims to have completed the retention of the collateral pledged by the junior mezzanine borrower, and therefore, the Company's interest in the 111 West 57th Street Property. The carrying value of the Company's equity investment in the 111 West 57^th Property represented a substantial portion of the Company's assets and net equity value.

The Company has an appeal pending on its challenge to the Strict Foreclosure, which has not yet been resolved. The Company is currently attempting to have the Appellate Division declare the Strict Foreclosure invalid and to enjoin the Strict Foreclosure. The Company moved for a stay or injunctive relief pending appeal, and that motion was denied by the appellate court on January 18, 2018.

Since the Company is not party to the Loan Agreements, it does not have access to communications with the lenders, except for those individual communications the Sponsors have elected to share. The Company has continued to demand access to such information, including access to the books and records for the 111 West 57^th Property both under the JV Agreement and as part of the 111 West 57^th Action and the 111 West 57^th Spruce Action.

For additional information with regard to the Company's recording of an impairment of its equity investment in the 111 West 57^th Property; see Note 4. The carrying value of the Company's equity investment in the 111 West 57^th Property represented substantially all of the Company's assets and net equity value.

For information relating to the Litigation Funding Agreement entered into between the Company and Mr. Richard A. Bianco, the Company's President and Chief Executive Officer, see Note 10.

With respect to its disputes and litigation relating to its interest in the 111 West 57th Property, the Company is continuing to pursue various legal courses of action, as well as considering other possible economic strategies, including the possible sale of the Company's interest in and/or rights with respect to the 111 West 57th Property. The Company is continuing to pursue other options to realize the Company's investment value and/or protect its legal rights.

The Company can give no assurances regarding the outcome of the matters described herein, including as to the effect of Spruce's actions described herein, whether the Sponsors will perform their contractual commitments to the Company under the JV Agreement, as to what further action, if any, the lenders may take with respect to the project, as to the ultimate resolution of the ongoing litigation proceedings relating to the Company's investment interest in the 111 West 57^th Property, as to the ultimate effect of the Sponsors', the Company's or the lenders' actions on the project, as to the completion or ultimate success of the project, or as to the value or ultimate realization of any portion of the Company's equity investment in the 111 West 57^th Street Property. For additional information on the Company's investment in the 111 West 57^th Property and the Company's legal actions related thereto, see Note 9.

While the Company's management is evaluating future courses of action to protect and/or recover the value of the Company's equity investment in the 111 West 57^th Property, the adverse developments make it uncertain as to whether any such courses of action will be successful. Any such efforts are likely to require sustained effort over a period of time, and require substantial additional financial resources. Inability to recover all or most of such value would in all likelihood have a material adverse effect on the Company's financial condition and future prospects.

IsZo Capital L.P. derivatively and on behalf of AmBase Corporation v. Richard A. Bianco, et al. In February 2018, IsZo Capital L.P. commenced an action, IsZo Capital L.P. derivatively and on behalf of AmBase Corporation v. Richard A. Bianco, et al., Index No. 650812/2018 in the New York State Supreme Court for New York County (the "IsZo Capital L.P. action"). The defendants in the action include all officers and directors of AmBase Corporation and AmBase Corporation as a nominal defendant. The plaintiff alleges various breaches of fiduciary duty against all of the directors and officers concerning the decisions made in the 111 West 57^th Street Property investment and a certain litigation funding agreement. IsZo Capital L.P. also seeks declaratory judgment relief concerning a litigation funding agreement and the 111 West 57^th Street Property. AmBase and the officers and directors intend to vigorously defend themselves and will move to dismiss the Complaint when all of the officers and directors have been served with the Summons and Complaint. The Company can give no assurances regarding the outcome of the matters described herein.