Segment Reporting (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2024 USD ($)	Sep. 30, 2024 USD ($)	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Number of Reportable Segments									2
Net premiums earned	$ 18,931	$ 27,441	$ 27,054	$ 25,579	$ 24,945	$ 12,187	$ 7,785	$ 6,995	$ 99,005	$ 51,911	$ 13,869
Commission income	38,009	23,064	13,221	17,729	12,191	14,572	10,032	14,486	92,023	51,281	30,695
Program fees	3,989	3,622	3,328	2,567	2,461	2,415	2,076	1,485	13,506	8,437	3,095
Revenues from external customers									92,023	51,281	30,695
Net investment income, net investment gains (losses), including impairments									13,951	13,176	4,442
Net gains (losses) on derivative contracts	(2,043)	6,545	(438)	(48)	69	(27)	(146)	(175)	4,016	(279)	935
Other income (expense)									13,314	200	576
Total revenues and other income									235,815	124,728	53,612
Loss and loss adjustment expenses (benefit)	9,826	20,421	23,024	19,355	16,805	9,509	5,739	4,659	72,626	36,712	9,071
Policy acquisition costs	7,850	5,993	5,399	4,424	5,851	1,956	1,351	1,399	23,666	10,557	2,535
Commission expenses	13,667	9,499	7,888	9,822	7,392	8,455	6,021	7,597	40,876	29,465	17,641
Depreciation expense									2,345	1,078	872
Amortization of intangible assets	8,901	6,423	1,139	1,139	1,139	1,079	966	967	17,602	4,152	2,921
EBITDA	(30,518)				(18,991)				(30,518)	(18,991)	(31,913)
Other Comprehensive Income (losss) Net of Tax Portion Attributable to Noncontrolling Interest EBITDA Adjusted									(6,448)	(2,102)	(1,463)
AMBAC EBITDA	(36,966)				(21,093)				(36,966)	(21,093)	(33,377)
Interest expense									9,379	0	0
Compensation expense									64,346	48,468	39,159
Non Compensation expense									64,820	18,517	17,119
Total expenses									295,660	148,949	89,318
Pretax income (loss) from continuing operations									(59,845)	(24,221)	(35,706)
Segment income tax expense (benefit)									(924)	(989)	(462)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total	(20,943)	(19,890)	(14,719)	(3,369)	(9,099)	(4,595)	(8,725)	(813)	(58,921)	(23,232)	(35,244)
Noncontrolling interest									(361)	(1,319)	(871)
Segment net income (loss) attributable to Ambac shareholders									(59,282)	(24,551)	(36,115)
Discontinued operations	(526,102)	$ (9,387)	$ 14,182	$ 24,140	7,169	$ 66,190	$ (9,300)	$ (35,876)	(497,167)	28,183	557,364
Net income (loss) attributable to Ambac shareholders									(556,449)	3,632	522,380
Assets	8,058,378				8,428,320				8,058,378	8,428,320	7,972,730
Disposal Group, Including Discontinued Operation, Assets	6,267,200				7,516,456				6,267,200	7,516,456	7,291,949
Corporate Expenses Changed to Discontinued Operations									14,919	19,367	20,189
United States [Member]
Total revenues and other income									212,605	124,728	53,612
United Kingdom [Member]
Total revenues and other income									23,210	0	0
Specialty Property & Casualty Program
Net premiums earned									99,005	51,911	13,869
Program fees									13,506	8,437	3,095
Net investment income, net investment gains (losses), including impairments									6,400	3,759	1,559
Net gains (losses) on derivative contracts									0	0
Other income (expense)									7,409	(6)	(58)
Total revenues and other income									126,320	64,101	18,465
Loss and loss adjustment expenses (benefit)									72,626	36,712	9,071
Policy acquisition costs									23,666	10,557	2,535
Depreciation expense									0	0	0
EBITDA	12,222				383				12,222	383	(6,346)
AMBAC EBITDA	12,222				383				12,222	383	(6,347)
Interest expense											0
Compensation expense									10,201	10,853	7,799
Non Compensation expense									7,605	5,596	5,406
Total expenses									114,098	63,718	24,811
Pretax income (loss) from continuing operations									12,222	383	(6,346)
Segment income tax expense (benefit)									1,753	48	(1)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total									10,469	335	(6,345)
Noncontrolling interest									2	(1)	15
Segment net income (loss) attributable to Ambac shareholders									10,471	334	(6,330)
Assets	751,272				523,179				751,272	523,179	316,327
Insurance Distribution
Commission income									92,023	51,281	30,695
Net investment income, net investment gains (losses), including impairments									787	64	0
Net gains (losses) on derivative contracts									106	0
Other income (expense)									6,320	200	715
Total revenues and other income									99,236	51,546	31,410
Commission expenses									40,876	29,465	17,641
Depreciation expense									481	42	31
Operating Expenses										0
Amortization of intangible assets									17,602	4,152	2,921
EBITDA	19,653				11,483				19,653	11,483	7,476
Other Comprehensive Income (losss) Net of Tax Portion Attributable to Noncontrolling Interest EBITDA Adjusted									(6,448)	(2,102)	(1,463)
AMBAC EBITDA	13,208								13,208		6,013
Interest expense									9,379		0
Compensation expense									28,353	7,951	4,518
Non Compensation expense									10,354	2,647	1,775
Total expenses									107,045	44,257	26,886
Pretax income (loss) from continuing operations									(7,809)	7,289	4,524
Segment income tax expense (benefit)									(928)	156	0
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total									(6,881)	7,133	4,524
Noncontrolling interest									(363)	(1,318)	(886)
Segment net income (loss) attributable to Ambac shareholders									(7,244)	5,815	3,638
Assets	900,222				154,846				900,222	154,846	138,068
Continuing Operations
Assets	1,791,178				911,864				1,791,178	911,864	680,781
Corporation
Net investment income, net investment gains (losses), including impairments											2,883
Net gains (losses) on derivative contracts											935
Other income (expense)											(81)
Total revenues and other income											3,737
Depreciation expense											841
EBITDA											(33,043)
AMBAC EBITDA											(33,043)
Compensation expense											26,842
Non Compensation expense											9,938
Total expenses											37,621
Pretax income (loss) from continuing operations											(33,884)
Segment income tax expense (benefit)											(462)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total											(33,422)
Segment net income (loss) attributable to Ambac shareholders											(33,422)
Assets											$ 226,386
Corporate Segment
Net investment income, net investment gains (losses), including impairments									6,764	9,353
Net gains (losses) on derivative contracts									3,910	(279)
Other income (expense)									(415)	6
Total revenues and other income									10,259	9,080
Depreciation expense									1,864	1,036
EBITDA	(62,393)				(30,858)				(62,393)	(30,858)
AMBAC EBITDA	(62,396)				(30,858)				(62,396)	(30,858)
Compensation expense									25,791	29,664
Non Compensation expense									46,861	10,274
Total expenses									74,516	40,974
Pretax income (loss) from continuing operations									(64,257)	(31,894)
Segment income tax expense (benefit)									(1,748)	(1,193)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total									(62,509)	(30,701)
Segment net income (loss) attributable to Ambac shareholders									(62,509)	(30,701)
Assets	$ 139,684				233,839				$ 139,684	233,839
Income Loss On Variable Interest Entities [Member]
AMBAC EBITDA					$ 9,381					$ 9,381