Schedule II - Condensed Financial Information of Registrant - Condensed Balance Sheet Schedule II - Condensed Financial Information of Registrant - Additional Information (Notes)	12 Months Ended
Dec. 31, 2017
Condensed Financial Information of Parent Company Only Disclosure [Text Block]	AMBAC FINANCIAL GROUP, INC. AND SUBSIDIARIES SCHEDULE II— CONDENSED FINANCIAL INFORMATION OF REGISTRANT (PARENT COMPANY ONLY) Notes to Condensed Financial Information (Dollar Amounts in Thousands) The condensed financial information of Ambac Financial Group, Inc. (“Ambac” or the “Registrant”) as of December 31, 2017 and 2016 and for the three years in the period ended December 31, 2017, should be read in conjunction with the consolidated financial statements of Ambac Financial Group, Inc. and Subsidiaries and the notes thereto included in this 2017 Annual Report on Form 10-K for the year ended December 31, 2017. Ambac, headquartered in New York City, is a financial services holding company incorporated in the state of Delaware on April 29, 1991. On May 1, 2013, Ambac emerged from Chapter 11 bankruptcy protection when the Second Modified Fifth Amended Plan of Reorganization of Ambac (the “Reorganization Plan”) became effective. On December 26, 2013, the United States Bankruptcy Court for the Southern District of New York (the “Bankruptcy Court”) entered an order of final decree closing Ambac’s Chapter 11 case. Ambac filed a voluntary petition for relief under Chapter 11 of the United States Bankruptcy Code in the Bankruptcy Court on November 8, 2010. Income Taxes Ambac files a consolidated Federal income tax return with its U.S. subsidiaries. Ambac and its subsidiaries also file separate or combined income tax returns in various states, local and foreign jurisdictions. As of December 31, 2017 Ambac had a U.S. loss carryforwards totaling $3,694,844, which, if not utilized, will begin expiring in 2029, and will fully expire in 2032. The NOL allocable to AFG as of December 31, 2017 is $1,412,639. Pursuant to the Amended TSA, to the extent Ambac Assurance generated taxable income after September 30, 2011, which offset the allocated $3,650,000 of NOLs, (or the proportionate amount of AMT NOL (as defined)), it is obligated to make payments (“Tolling Payments”), subject to certain credits, to the Registrant in accordance with a four Tier, A through D, NOL usage table. NOLs in excess of the allocated $3,650,000 may be utilized beginning in 2016, subject to the Registrant's consent, not to be unreasonably withheld, for a payment of 25% of the benefit received. Ambac Assurance has utilized all of its current post determination date NOLs generated from September 30, 2011 through December 31, 2017 (post determination date NOLs); however, additional post determination date NOLs may be generated in the future. During this time period, Ambac Assurance's cumulative net taxable income was approximately $1,367,795, which utilized all of the $479,000 allocated Tier A NOL and $888,795 of the $1,057,000 allocated Tier B NOL and resulted in accrued Tolling Payments, net of applicable credits. At December 31, 2017, $30,496 of Tolling Payments are due to Ambac no later than forty-five days after April 15, 2018. Of the bankruptcy related credits available to offset the first $5,000 of payments due under each of the NOL usage Tiers A, B, and C, Ambac Assurance has fully utilized the combined $10,000 of Tier A and Tier B credits.

Schedule II - Condensed Financial Information of Registrant - Condensed Balance Sheet Schedule II - Condensed Financial Information of Registrant - Additional Information (Notes)

12 Months Ended

Dec. 31, 2017

Condensed Financial Information of Parent Company Only Disclosure [Text Block]

AMBAC FINANCIAL GROUP, INC. AND SUBSIDIARIES

SCHEDULE II— CONDENSED FINANCIAL INFORMATION

OF REGISTRANT (PARENT COMPANY ONLY)

Notes to Condensed Financial Information

(Dollar Amounts in Thousands)

The condensed financial information of Ambac Financial Group, Inc. (“Ambac” or the “Registrant”) as of December 31, 2017 and 2016 and for the three years in the period ended December 31, 2017, should be read in conjunction with the consolidated financial statements of Ambac Financial Group, Inc. and Subsidiaries and the notes thereto included in this 2017 Annual Report on Form 10-K for the year ended December 31, 2017.

Ambac, headquartered in New York City, is a financial services holding company incorporated in the state of Delaware on April 29, 1991. On May 1, 2013, Ambac emerged from Chapter 11 bankruptcy protection when the Second Modified Fifth Amended Plan of Reorganization of Ambac (the “Reorganization Plan”) became effective. On December 26, 2013, the United States Bankruptcy Court for the Southern District of New York (the “Bankruptcy Court”) entered an order of final decree closing Ambac’s Chapter 11 case. Ambac filed a voluntary petition for relief under Chapter 11 of the United States Bankruptcy Code in the Bankruptcy Court on November 8, 2010.

Income Taxes

Ambac files a consolidated Federal income tax return with its U.S. subsidiaries. Ambac and its subsidiaries also file separate or combined income tax returns in various states, local and foreign jurisdictions. As of December 31, 2017 Ambac had a U.S. loss carryforwards totaling $3,694,844, which, if not utilized, will begin expiring in 2029, and will fully expire in 2032. The NOL allocable to AFG as of December 31, 2017 is $1,412,639.

Pursuant to the Amended TSA, to the extent Ambac Assurance generated taxable income after September 30, 2011, which offset the allocated $3,650,000 of NOLs, (or the proportionate amount of AMT NOL (as defined)), it is obligated to make payments (“Tolling Payments”), subject to certain credits, to the Registrant in accordance with a four Tier, A through D, NOL usage table. NOLs in excess of the allocated $3,650,000 may be utilized beginning in 2016, subject to the Registrant's consent, not to be unreasonably withheld, for a payment of 25% of the benefit received.

Ambac Assurance has utilized all of its current post determination date NOLs generated from September 30, 2011 through December 31, 2017 (post determination date NOLs); however, additional post determination date NOLs may be generated in the future. During this time period, Ambac Assurance's cumulative net taxable income was approximately $1,367,795, which utilized all of the $479,000 allocated Tier A NOL and $888,795 of the $1,057,000 allocated Tier B NOL and resulted in accrued Tolling Payments, net of applicable credits. At December 31, 2017, $30,496 of Tolling Payments are due to Ambac no later than forty-five days after April 15, 2018. Of the bankruptcy related credits available to offset the first $5,000 of payments due under each of the NOL usage Tiers A, B, and C, Ambac Assurance has fully utilized the combined $10,000 of Tier A and Tier B credits.

- Definition

The entire disclosure for condensed financial information, including the financial position, cash flows, and the results of operations of the registrant (parent company) as of the same dates or for the same periods for which audited consolidated financial statements are being presented. Alternatively, the details of this disclosure can be reported by the specific parent company taxonomy elements, indicating the appropriate date and period contexts in an instance document.

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