Legal Proceedings	6 Months Ended
Jun. 30, 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 a lawsuit 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 are 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, among other claims, that the Defendants engaged in an unlawful scheme to dilute AmBase's equity interest in the joint real estate venture 111 West 57^th Partners, to develop the 111 West 57^th Street Property and to keep for themselves certain financing opportunities in breach of Defendants' contractual and fiduciary duties. The complaint also alleges that defendants have failed 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, an accounting and a constructive trust over distributions received by the Defendants. The complaint in this action has been filed, a motion to dismiss is pending and discovery is ongoing The Company has also demanded from the Sponsors access to the books and records for the 111 West 57^th Property which the Sponsors have refused, claiming they have provided all books and records as required. 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 TRO 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. On July 26, 2017, the Court issued a temporary restraining order barring Spruce from accepting the collateral pending a preliminary injunction hearing scheduled for August 14, 2017. For additional information on the events leading to this litigation see Note 4. 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 both under the JV Agreement and as part of the 111 West 57^th Action and the 111 West 57^th Spruce Action. With respect to its current disputes and litigation relating to its interest in the 111 West 57th Property, the Company will continue to pursue all available legal courses of action as well as considering other possible economic strategies, including the possible sale of the Company's investment interest in the 111 West 57th Property. The Company is negotiating with all potential parties to protect the Company's interests. Additionally, the Company is pursuing alternative financial resources to help finance current and future litigation in the courts to protect the Company's investment value, including negotiating possible contingency arrangements with legal counsel and/or raising capital for the Company to pursue its legal rights. For additional information with regard to, among other items, recent developments concerning the Company's investment in the 111 West 57^th Property, information concerning the junior mezzanine lender declaration of an event of default and its proposal to take control of the collateral pledged by the junior mezzanine borrower and therefore, the Company's entire interest in the 111 West 57th Street Property, the Company's request for injunctive relief, and the NY Court's issuance of a temporary restraining order pending a preliminary injunction hearing, see Note 4 and Note 11. The Company can give no assurances regarding the outcome of the matters described above, including as to 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, or as to the ultimate effect of the Sponsors', the Company's or the lenders' actions on the project, or as to the completion or ultimate success of the project, or the value or ultimate realization of any portion of the Company's equity interest in the 111 West 57^th Street Property. For additional information on the Company's investment in the 111 West 57^th Property see Note 4 and Note 11.

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 a lawsuit 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 are 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, among other claims, that the Defendants engaged in an unlawful scheme to dilute AmBase's equity interest in the joint real estate venture 111 West 57^th Partners, to develop the 111 West 57^th Street Property and to keep for themselves certain financing opportunities in breach of Defendants' contractual and fiduciary duties. The complaint also alleges that defendants have failed 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, an accounting and a constructive trust over distributions received by the Defendants. The complaint in this action has been filed, a motion to dismiss is pending and discovery is ongoing The Company has also demanded from the Sponsors access to the books and records for the 111 West 57^th Property which the Sponsors have refused, claiming they have provided all books and records as required.

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 TRO 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. On July 26, 2017, the Court issued a temporary restraining order barring Spruce from accepting the collateral pending a preliminary injunction hearing scheduled for August 14, 2017. For additional information on the events leading to this litigation see Note 4.

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 both under the JV Agreement and as part of the 111 West 57^th Action and the 111 West 57^th Spruce Action.

With respect to its current disputes and litigation relating to its interest in the 111 West 57th Property, the Company will continue to pursue all available legal courses of action as well as considering other possible economic strategies, including the possible sale of the Company's investment interest in the 111 West 57th Property. The Company is negotiating with all potential parties to protect the Company's interests. Additionally, the Company is pursuing alternative financial resources to help finance current and future litigation in the courts to protect the Company's investment value, including negotiating possible contingency arrangements with legal counsel and/or raising capital for the Company to pursue its legal rights.

For additional information with regard to, among other items, recent developments concerning the Company's investment in the 111 West 57^th Property, information concerning the junior mezzanine lender declaration of an event of default and its proposal to take control of the collateral pledged by the junior mezzanine borrower and therefore, the Company's entire interest in the 111 West 57th Street Property, the Company's request for injunctive relief, and the NY Court's issuance of a temporary restraining order pending a preliminary injunction hearing, see Note 4 and Note 11.

The Company can give no assurances regarding the outcome of the matters described above, including as to 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, or as to the ultimate effect of the Sponsors', the Company's or the lenders' actions on the project, or as to the completion or ultimate success of the project, or the value or ultimate realization of any portion of the Company's equity interest in the 111 West 57^th Street Property. For additional information on the Company's investment in the 111 West 57^th Property see Note 4 and Note 11.