Schedule II - Condensed Financial Information of Registrant (Parent Company Only) - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Cash flows from operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total	$ (95,803)	$ (58,921)	$ (23,232)
Adjustments to reconcile net income loss to net cash used in operating activities:
Share-based compensation	9,707	9,356	12,266
Proceeds from Contributions from Affiliates	15,343	10,739	8,032
Other, net	(11,343)	6,158	(7,829)
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]
Proceeds from matured bonds	37,658	21,580	15,078
Purchases of bonds	(25,577)	(60,470)	(33,243)
Change in short-term investments	(18,752)	101,829	4,157
Proceeds from Sale and Maturity of Other Investments	0	625	0
Other, net	(10,053)	(3,750)	(4,854)
Cash flows from financing activities:
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation	21,355	28,610	(717)
Cash paid during the period for:
Payments to Acquire Businesses, Net of Cash Acquired	217,940	243,776	6,953
Payments for Repurchase of Common Stock	29,942	11,698	4,510
Stock Issued During Period, Value, Acquisitions		29,229
Ambac Financial Group, Inc Parent Company Only [Member]
Cash flows from operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total	(261,692)	(556,449)	3,632
Adjustments to reconcile net income loss to net cash used in operating activities:
Equity in undistributed net (income) loss of non-debtor subsidiaries	15,020	29,770	(15,027)
Decrease in current income taxes payable	1,613	(1,970)	(1,674)
Share-based compensation	9,707	8,361	9,404
Decrease in other assets	26,256	7,817	(4,660)
Other, net	(128)	2,312	2,337
Net cash provided by (used in) operating activities	(30,593)	(2,253)	2,044
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]
Proceeds from matured bonds	1,305	5,000	0
Purchases of bonds	(1,446)	0	(795)
Change in short-term investments	25,095	91,249	19,676
Proceeds from Sale and Maturity of Other Investments	3,146	(1,749)	(2,715)
Net Cash Provided by (Used in) Investing Activities, Total	428,285	94,500	16,166
Capital Contribution to Subsidiaries	(384,604)	(70,817)	(16,050)
Cash flows from financing activities:
Cash Provided by (Used in) Financing Activity, Including Discontinued Operation	(397,546)	(82,516)	(20,560)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Excluding Exchange Rate Effect	146	9,731	(2,350)
Cash and cash equivalents at beginning of period	9,981	250	2,600
Cash and cash equivalents end of period	10,127	9,981	250
Cash paid during the period for:
Income taxes	0	0	0
Payments for Repurchase of Common Stock	(29,942)	(11,699)	(4,510)
Parent [Member]
Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]
Other, net	$ (7,115)	$ 0	$ 0