Special Purpose Entities, Including Variable Interest Entities - Summary of Carrying Amount of Assets, Liabilities and Maximum Exposure to Loss of Ambac's Variable Interests in Non-Consolidated Variable Interest Entities (Detail) - Variable Interest Entity [Member] - Successor [Member] - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Global Public Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	$ 28,586,582	$ 31,639,004
Insurance Assets	377,412	457,774
Insurance Liabilities	427,299	533,192
Derivative Liabilities	(24,860)	(22,135)
Collateralized Debt Obligations [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	980,935	1,386,100
Insurance Assets	264	345
Insurance Liabilities	3,639	4,000
Derivative Liabilities	(129,525)	(145,565)
Residential Mortgage-Backed Securities [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	17,081,002	16,202,408
Insurance Assets	1,279,650	1,011,888
Insurance Liabilities	2,680,739	2,924,987
Other Consumer Asset-Backed [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	3,853,443	5,109,776
Insurance Assets	47,346	65,204
Insurance Liabilities	535,090	885,572
Derivative Liabilities	0	(36,877)
Other Commercial Asset-Backed [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	2,393,805	3,119,891
Insurance Assets	104,033	135,215
Insurance Liabilities	94,191	128,988
Derivative Liabilities	0	0
Other [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	3,286,568	3,801,382
Insurance Assets	81,017	97,345
Insurance Liabilities	461,364	599,915
Derivative Liabilities	$ 16,604	$ 18,176