Net Income Per Share - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Nov. 12, 2024	May 05, 2022	Mar. 29, 2022	Apr. 30, 2013
Schedule Of Earnings Per Share [Line Items]
Common Stock, Shares, Outstanding	46,506,973
Number of new common stock issued	48,875,167	46,659,144
Common stock, par value (in dollars per share)							$ 0.01
Net income (loss) attributable to Ambac shareholders	$ (556,449)	$ 3,632	$ 522,380
Noncontrolling Interest, Change in Redemption Value	49,966	4,836	2,504
Share Repurchase Program, Authorized, Amount				$ 50,000	$ 15,000	$ 20,000
Payments for Repurchase of Common Stock	11,698	$ 4,510	$ 14,217
Share Repurchase Program, Remaining Authorized, Amount	$ 38,302
Treasury Stock, Shares, Acquired	937,141	325,068	1,605,316
Treasury Stock, Value, Acquired, Cost Method	$ 11,699	$ 4,510	$ 14,217
Shares Acquired, Average Cost Per Share	$ 12.48	$ 13.88	$ 8.86
Common Stock [Member]
Schedule Of Earnings Per Share [Line Items]
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture	1,311,603