Organization and Going Concern	12 Months Ended
Dec. 31, 2017
Organization and Going Concern [Abstract]
Organization and Going Concern	Note 1 – Organization and Going Concern AmBase Corporation (the "Company" or "AmBase") is a Delaware corporation that was incorporated in 1975. AmBase is a holding company. At December 31, 2017, the Company's assets consisted primarily of cash and cash equivalents, real estate owned and a deferred tax asset. On January 26, 2018, the Company sold its commercial office building in Greenwich, Connecticut, see Note 3 herein for additional information. See Note 8 for additional information regarding taxes. The Company is engaged in the management of its assets and liabilities. In June 2013, the Company purchased an equity interest in a real estate development property through a joint venture agreement to purchase and develop real property located at 105 through 111 West 57^th Street in New York, New York (the "111 West 57^th Property"). The Company has also made significant investments in the 111 West 57th Street Property in 2013, 2014 and 2015. The Company is engaged in material disputes and litigation with the sponsors of the joint venture (the "Sponsor") and a mezzanine lender to the joint venture ("Spruce"). 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 Company recorded an impairment of its equity investment in the 111 West 57th Property in the full year period ended December 31, 2017. 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. As noted above, despite ongoing litigation challenging the legitimacy of the actions taken by the Sponsors and Spruce in connection with the Company's investment in the 111 West 57^th Property as further discussed herein, in accordance with GAAP, the Company recorded an impairment of its equity investment in the 111 West 57th Property in the full year period ended December 31, 2017. The Company is and will continue to pursue the recovery of its asset value from various sources of recovery; however, there can be no assurance that the Company will prevail with respect to any of its claims. For additional information with regard to the Company's legal proceedings related to the 111 West 57^th Property, see Note 4 and Note 9 herein. 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. See Note 4 and Note 9 herein for additional information concerning the Company's pending appeal of its challenge to the Strict Foreclosure and the Company's recording of an impairment of its equity investment in the 111 West 57^th Property. A fundamental principle of the preparation of financial statements in accordance with GAAP is the assumption that an entity will continue in existence as a going concern, which contemplates continuity of operations and the realization of assets and settlement of liabilities occurring in the ordinary course of business. In accordance with this requirement, the Company has prepared its accompanying consolidated financial statements assuming the Company will continue as a going concern. The Company has incurred operating losses and used cash for operating activities for the past several years. In June 2013, the Company purchased an equity interest in a real estate development property through a joint venture agreement to purchase and develop real property located at 105 through 111 West 57^th Street in New York, New York (the "111 West 57^th Property"). The Company has also made significant investments in the 111 West 57th Street Property in 2013, 2014 and 2015. The Company is engaged in material disputes and litigation with the sponsors of the joint venture (the "Sponsor") and a mezzanine lender to the joint venture ("Spruce"). The Company recorded an impairment of its equity investment in the 111 West 57th Property in the full year period ended December 31, 2017. See Note 4 and Note 9 to the Company's consolidated financial statements for additional information regarding this impairment charge and the legal proceedings relating to the Company's investment in the 111 West 57^th 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 has continued to keep operating expenses at a reduced level; however, there can be no assurance that the Company's current level of operating expenses will not increase or that other uses of cash will not be necessary. The Company believes that based on its current level of operating expenses, its currently available cash and financial resources together with the net proceeds from the sale of its commercial office building in Greenwich, Connecticut as further discussed in Note 3 herein, may not be sufficient to cover operating cash needs through the twelve month period from the financial statement reporting date. Based on the above factors, management determined there is substantial doubt about the Company's ability to continue as a going concern within one year after the date that the financial statements are issued. The accompanying consolidated financial statements have been prepared assuming that the Company will continue as a going concern. The financial statements do not include adjustments to the carrying value of assets and liabilities which might be necessary should the Company not continue in operation. Over the next several months, the Company will seek to manage its current level of cash and cash equivalents, through various ways, including but not limited to, reducing operating expenses, possible asset sales and/or long term borrowings which may include additional borrowings from affiliates of the Company, although this cannot be assured. In order to continue on a long-term basis, the Company must raise additional capital through the sale of assets or long term borrowings. There can be no assurance that the Company will be able to sell any of its assets or attain such financing at terms acceptable to the Company, if at all. In September 2017, the Company and Mr. Richard A. Bianco, the Company's Chairman, President and Chief Executive Officer ("R. A. Bianco") entered into an agreement pursuant to which Mr. R. A. Bianco will fund the Company's litigation expenses in connection with the 111 West 57^th Property (the "Litigation Funding Agreement"). For additional information including the terms of the Litigation Funding Agreement, see Note 10 herein. 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 4 and 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. In May 2016, the Company and Mr. R. A. Bianco entered into an agreement for Mr. R. A. Bianco to provide to the Company a secured working capital line of credit. Pursuant to this agreement, Mr. Bianco has made several loans to the Company, for use as working capital. On January 26, 2018, in connection with the sale by the Company of its office building in Greenwich, Connecticut, the Company repaid the full amount of the working capital loan, plus accrued interest to Mr. R. A. Bianco, and in connection therewith the working capital line of credit was terminated. For additional information, see Note 12 herein.

Note 1 – Organization and Going Concern

AmBase Corporation (the "Company" or "AmBase") is a Delaware corporation that was incorporated in 1975. AmBase is a holding company.

At December 31, 2017, the Company's assets consisted primarily of cash and cash equivalents, real estate owned and a deferred tax asset. On January 26, 2018, the Company sold its commercial office building in Greenwich, Connecticut, see Note 3 herein for additional information. See Note 8 for additional information regarding taxes. The Company is engaged in the management of its assets and liabilities.

In June 2013, the Company purchased an equity interest in a real estate development property through a joint venture agreement to purchase and develop real property located at 105 through 111 West 57^th Street in New York, New York (the "111 West 57^th Property"). The Company has also made significant investments in the 111 West 57th Street Property in 2013, 2014 and 2015. The Company is engaged in material disputes and litigation with the sponsors of the joint venture (the "Sponsor") and a mezzanine lender to the joint venture ("Spruce"). 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 Company recorded an impairment of its equity investment in the 111 West 57th Property in the full year period ended December 31, 2017. 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.

As noted above, despite ongoing litigation challenging the legitimacy of the actions taken by the Sponsors and Spruce in connection with the Company's investment in the 111 West 57^th Property as further discussed herein, in accordance with GAAP, the Company recorded an impairment of its equity investment in the 111 West 57th Property in the full year period ended December 31, 2017. The Company is and will continue to pursue the recovery of its asset value from various sources of recovery; however, there can be no assurance that the Company will prevail with respect to any of its claims. For additional information with regard to the Company's legal proceedings related to the 111 West 57^th Property, see Note 4 and Note 9 herein.

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. See Note 4 and Note 9 herein for additional information concerning the Company's pending appeal of its challenge to the Strict Foreclosure and the Company's recording of an impairment of its equity investment in the 111 West 57^th Property.

A fundamental principle of the preparation of financial statements in accordance with GAAP is the assumption that an entity will continue in existence as a going concern, which contemplates continuity of operations and the realization of assets and settlement of liabilities occurring in the ordinary course of business. In accordance with this requirement, the Company has prepared its accompanying consolidated financial statements assuming the Company will continue as a going concern.

The Company has incurred operating losses and used cash for operating activities for the past several years. In June 2013, the Company purchased an equity interest in a real estate development property through a joint venture agreement to purchase and develop real property located at 105 through 111 West 57^th Street in New York, New York (the "111 West 57^th Property"). The Company has also made significant investments in the 111 West 57th Street Property in 2013, 2014 and 2015. The Company is engaged in material disputes and litigation with the sponsors of the joint venture (the "Sponsor") and a mezzanine lender to the joint venture ("Spruce"). The Company recorded an impairment of its equity investment in the 111 West 57th Property in the full year period ended December 31, 2017. See Note 4 and Note 9 to the Company's consolidated financial statements for additional information regarding this impairment charge and the legal proceedings relating to the Company's investment in the 111 West 57^th 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 has continued to keep operating expenses at a reduced level; however, there can be no assurance that the Company's current level of operating expenses will not increase or that other uses of cash will not be necessary. The Company believes that based on its current level of operating expenses, its currently available cash and financial resources together with the net proceeds from the sale of its commercial office building in Greenwich, Connecticut as further discussed in Note 3 herein, may not be sufficient to cover operating cash needs through the twelve month period from the financial statement reporting date. Based on the above factors, management determined there is substantial doubt about the Company's ability to continue as a going concern within one year after the date that the financial statements are issued. The accompanying consolidated financial statements have been prepared assuming that the Company will continue as a going concern. The financial statements do not include adjustments to the carrying value of assets and liabilities which might be necessary should the Company not continue in operation.

Over the next several months, the Company will seek to manage its current level of cash and cash equivalents, through various ways, including but not limited to, reducing operating expenses, possible asset sales and/or long term borrowings which may include additional borrowings from affiliates of the Company, although this cannot be assured. In order to continue on a long-term basis, the Company must raise additional capital through the sale of assets or long term borrowings. There can be no assurance that the Company will be able to sell any of its assets or attain such financing at terms acceptable to the Company, if at all.

In September 2017, the Company and Mr. Richard A. Bianco, the Company's Chairman, President and Chief Executive Officer ("R. A. Bianco") entered into an agreement pursuant to which Mr. R. A. Bianco will fund the Company's litigation expenses in connection with the 111 West 57^th Property (the "Litigation Funding Agreement"). For additional information including the terms of the Litigation Funding Agreement, see Note 10 herein.

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 4 and 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.

In May 2016, the Company and Mr. R. A. Bianco entered into an agreement for Mr. R. A. Bianco to provide to the Company a secured working capital line of credit. Pursuant to this agreement, Mr. Bianco has made several loans to the Company, for use as working capital. On January 26, 2018, in connection with the sale by the Company of its office building in Greenwich, Connecticut, the Company repaid the full amount of the working capital loan, plus accrued interest to Mr. R. A. Bianco, and in connection therewith the working capital line of credit was terminated. For additional information, see Note 12 herein.