Organization and Liquidity	12 Months Ended
Dec. 31, 2018
Organization and Liquidity [Abstract]
Organization and Liquidity	Note 1 – Organization and Liquidity AmBase Corporation (the “Company” or “AmBase”) is a Delaware corporation that was incorporated in 1975. AmBase is a holding company. At December 31, 2018, the Company’s assets consisted primarily of cash and cash equivalents and tax assets. On January 26, 2018, the Company sold its commercial office building in Greenwich, Connecticut, see Note 3 herein for additional information. The Company is engaged in the management of its assets and liabilities. In January 2019, the Company filed its 2018 federal income tax return seeking a refund of approximately $10.7 million of alternative minimum tax (“AMT”) credit carryforwards as provided for in the 2017 Tax Act (the “2017 Tax Act”). This amount is reflected as a federal tax receivable at December 31, 2018. The remaining amount of $10.7 million is reflected as a deferred tax asset at December 31, 2018, based on tax returns to be filed in future years. In March 2019, the Company received a $10.7 million federal tax refund based on the Company’s 2018 federal income tax return as filed. The Internal Revenue Service (“IRS”) typically has broad discretion to examine taxpayer tax returns, even after refunds have been paid to taxpayers, which could result in adjustments to AMT credit carryforward amounts refunded and/or claimed as refundable and/or AMT credit carryforward amounts ultimately received. See herein and Note 8, for additional information. 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 is engaged in material disputes and litigation with the sponsors of the joint venture (the “Sponsor”) and both mezzanine lenders to the joint venture (“Apollo” and “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. Despite ongoing litigation challenging the legitimacy of the actions taken by the Sponsor 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 2017. Prior to the Strict Foreclosure, 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 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. See Note 4 and Note 9 for additional information regarding the Company’s recording of an impairment of its equity investment in the 111 West 57^th Property and the Company’s legal proceedings relating to the 111 West 57^th Property, including the Company’s challenge to the Strict Foreclosure. The Company has incurred operating losses and used cash for operating activities for the past several years. 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. Management has determined that there is no longer substantial doubt about the Company's ability to continue as a going concern, due to the federal tax refund of $10.7 million received in March 2019. The Company believes that based on its current level of operating expenses its existing cash and cash equivalents, together with the March 2019 federal tax refund received, will be sufficient to fund operating activities for at least the next twelve months from the financial statement issuance date. The Company’s management expects that operating cash needs in 2019 will be met principally by the Company’s current financial resources, which include the federal tax refund of $10.7 million received in March 2019. Over the next several months, the Company will seek to manage its current level of cash and cash equivalents, including but not limited to reducing operating expenses and seeking recoveries from various sources, although this cannot be assured. In September 2017, the Company and Mr. Richard A. Bianco, the Company’s Chairman, President and Chief Executive Officer (“Mr. 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 Sponsor 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 Sponsor’s, 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. 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. R. A. Bianco has made several loans to the Company, for use as working capital. In January 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 11 herein.

Note 1 – Organization and Liquidity

AmBase Corporation (the “Company” or “AmBase”) is a Delaware corporation that was incorporated in 1975. AmBase is a holding company. At December 31, 2018, the Company’s assets consisted primarily of cash and cash equivalents and tax assets. On January 26, 2018, the Company sold its commercial office building in Greenwich, Connecticut, see Note 3 herein for additional information. The Company is engaged in the management of its assets and liabilities.

In January 2019, the Company filed its 2018 federal income tax return seeking a refund of approximately $10.7 million of alternative minimum tax (“AMT”) credit carryforwards as provided for in the 2017 Tax Act (the “2017 Tax Act”). This amount is reflected as a federal tax receivable at December 31, 2018. The remaining amount of $10.7 million is reflected as a deferred tax asset at December 31, 2018, based on tax returns to be filed in future years. In March 2019, the Company received a $10.7 million federal tax refund based on the Company’s 2018 federal income tax return as filed. The Internal Revenue Service (“IRS”) typically has broad discretion to examine taxpayer tax returns, even after refunds have been paid to taxpayers, which could result in adjustments to AMT credit carryforward amounts refunded and/or claimed as refundable and/or AMT credit carryforward amounts ultimately received. See herein and Note 8, for additional information.

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 is engaged in material disputes and litigation with the sponsors of the joint venture (the “Sponsor”) and both mezzanine lenders to the joint venture (“Apollo” and “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. Despite ongoing litigation challenging the legitimacy of the actions taken by the Sponsor 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 2017. Prior to the Strict Foreclosure, 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 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.

See Note 4 and Note 9 for additional information regarding the Company’s recording of an impairment of its equity investment in the 111 West 57^th Property and the Company’s legal proceedings relating to the 111 West 57^th Property, including the Company’s challenge to the Strict Foreclosure.

The Company has incurred operating losses and used cash for operating activities for the past several years. 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. Management has determined that there is no longer substantial doubt about the Company's ability to continue as a going concern, due to the federal tax refund of $10.7 million received in March 2019. The Company believes that based on its current level of operating expenses its existing cash and cash equivalents, together with the March 2019 federal tax refund received, will be sufficient to fund operating activities for at least the next twelve months from the financial statement issuance date. The Company’s management expects that operating cash needs in 2019 will be met principally by the Company’s current financial resources, which include the federal tax refund of $10.7 million received in March 2019. Over the next several months, the Company will seek to manage its current level of cash and cash equivalents, including but not limited to reducing operating expenses and seeking recoveries from various sources, although this cannot be assured.

In September 2017, the Company and Mr. Richard A. Bianco, the Company’s Chairman, President and Chief Executive Officer (“Mr. 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 Sponsor 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 Sponsor’s, 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.

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. R. A. Bianco has made several loans to the Company, for use as working capital. In January 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 11 herein.