Financial Guarantee Insurance Contracts - Summary of Information Related to Policies Currently Included in Ambac's Loss Reserves or Subrogation Recoverable (Phantom) (Detail) - Successor [Member] - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Loss Reserves Ceded To Reinsurers	$ 27,478	$ 44,059	$ 74,519	$ 100,355
Loss and loss expense reserves	4,303,547	4,088,106
Subrogation recoverable	(660,471)	(1,229,293)
Liability for Claims	3,643,076	2,858,813	3,491,862	$ 3,798,733
Ceded Loss And Loss Expenses Paid Not Yet Recovered	$ (162)	$ (60)	$ 4,789