Quarterly Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Quarterly Financial Information Disclosure [Abstract]
Premiums Written, Net	$ 59,988	$ 115,154	$ 111,206	$ 96,422	$ 90,736	$ 77,499	$ 53,229	$ 51,823
Premiums Written, Net	(2,608)	32,754	32,289	26,247	36,750	24,768	9,120	9,187	$ 88,682	$ 79,825	$ 28,553
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
Net investment income, net investment gains (losses), including impairments	3,557	3,488	3,763	3,640	3,588	3,663	3,027	2,881	14,448	13,159	4,503
Realized Investment Gains (Losses)	(4,455)	(577)	4,535	0	1	0	(20)	38	(497)	19	(62)
Net gains (losses) on derivative contracts	(2,043)	6,545	(438)	(48)	69	(27)	(146)	(175)	4,016	(279)	935
Other revenue	7,235	6,422	(426)	83	67	(5)	101	37	13,314	200	577
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
General and Administrative Expense	40,444	44,681	28,336	18,050	21,193	17,914	17,117	11,839	129,166	66,985	56,278
Amortization of intangible assets	8,901	6,423	1,139	1,139	1,139	1,079	966	967	17,602	4,152	2,921
Interest Expense, Interest-Bearing Liability	5,634	3,745
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest									(59,845)	(24,221)	(35,706)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(20,943)	(19,890)	(14,719)	(3,369)	(9,099)	(4,595)	(8,725)	(813)	(58,921)	(23,232)	(35,244)
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)	$ (548,265)	$ (27,504)	$ (750)	$ 20,070	$ (15,688)	$ 65,869	$ (13,132)	$ (33,417)	$ (556,088)	$ 4,951	$ 522,120
Earnings Per Share, Basic	$ (10.23)	$ (0.63)	$ (0.02)	$ 0.44	$ (0.24)	$ 1.44	$ (0.29)	$ (0.73)	$ (10.71)	$ 0.18	$ 11.48
Diluted	$ (10.23)	$ (0.63)	$ (0.02)	$ 0.44	$ (0.24)	$ 1.44	$ (0.29)	$ (0.73)	$ (10.71)	$ 0.18	$ 11.48
Net income (loss) attributable to Ambac shareholders									$ (556,449)	$ 3,632	$ 522,380
Adjustment for Redeemable NCI	$ 55,762	$ (2,402)	$ (184)	$ 53	$ 4,855	$ 19	$ (294)	$ 212	53,210	4,792	2,469
Noncontrolling interest									$ (361)	$ (1,319)	$ (871)
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.70	$ (0.43)	$ (0.33)	$ (0.09)	$ (0.10)	$ (0.11)	$ (0.20)	$ (0.03)	$ (0.13)	$ (0.43)	$ (0.74)
Income (Loss) from Continuing Operations, Per Diluted Share	0.70	(0.43)	(0.33)	(0.09)	(0.10)	(0.11)	(0.20)	(0.03)	(0.13)	(0.43)	(0.74)
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	(10.93)	(0.20)	0.31	0.53	(0.14)	1.55	(0.09)	(0.70)	(10.58)	0.62	12.22
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	$ (10.93)	$ (0.20)	$ 0.31	$ 0.53	$ (0.14)	$ 1.55	$ (0.09)	$ (0.70)	$ (10.58)	$ 0.62	$ 12.22
Numerator of basic and diluted EPS	$ (492,503)	$ (29,906)	$ (934)	$ 20,123	$ (10,833)	$ 65,888	$ (13,426)	$ (33,205)	$ (6,072)	$ (19,759)	$ (33,646)
Net income (loss) attributable to Ambac common stockholders									$ (59,282)	$ (24,551)	$ (36,115)