Financial Guarantee Insurance Contracts - Summary of Information Related to Policies Currently Included in Ambac's Loss Reserves or Subrogation Recoverable (Parenthetical) (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Loss Reserves Ceded To Reinsurers	$ 71,031
Successor [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Loss Reserves Ceded To Reinsurers	71,031	$ 100,355	$ 110,015	$ 122,357
Loss and loss expense reserves	4,367,414	4,752,007
Subrogation recoverable	(981,402)	(953,274)
Liability for Claims	3,386,012	3,798,733	5,588,171	$ 5,470,234
Ceded Loss And Loss Expenses Paid Not Yet Recovered	$ 4,974	$ (517)	$ (760)