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	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Apr. 30, 2013
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Loss Reserves Ceded To Reinsurers	$ 44,059	$ 100,355
Successor [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Loss Reserves Ceded To Reinsurers	44,059	100,355	$ 122,357	$ 138,155
Loss and loss expense reserves	4,088,106	4,752,007		6,106,345
Subrogation recoverable	(1,229,293)	(953,274)		(533,673)
Liability for Claims	2,858,813	3,798,733	5,470,234	$ 5,572,672
Ceded Loss And Loss Expenses Paid Not Yet Recovered	$ (60)	$ (517)	$ (1,108)