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 (Details) - Variable Interest Entity, Primary Beneficiary [Member] - Successor [Member] - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Variable Interest Entities [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	$ 61,408,345	$ 64,520,702
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Assets	1,744,659	1,767,771
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Liabilities	4,616,520	5,076,654
Variable Interest Entity Nonconsolidated Carrying Amount Derivative Net Assets Or Liabilities	(152,300)	(186,401)
Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	30,209,521	32,881,698
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Assets	1,301,788	1,309,997
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Liabilities	4,107,140	4,543,462
Variable Interest Entity Nonconsolidated Carrying Amount Derivative Net Assets Or Liabilities	(126,669)	(164,266)
Global Structured Finance [Member] | Collateralized Debt Obligations [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	1,137,110	1,386,100
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Assets	293	345
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Liabilities	3,809	4,000
Variable Interest Entity Nonconsolidated Carrying Amount Derivative Net Assets Or Liabilities	(111,540)	(145,565)
Global Structured Finance [Member] | Residential Mortgage-Backed Securities [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	18,372,639	19,464,549
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Assets	1,036,830	1,011,888
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Liabilities	2,843,210	2,924,987
Global Structured Finance [Member] | Other Consumer Asset Backed [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	4,385,269	5,109,776
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Assets	53,068	65,204
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Liabilities	681,834	885,572
Variable Interest Entity Nonconsolidated Carrying Amount Derivative Net Assets Or Liabilities	(31,013)	(36,877)
Global Structured Finance [Member] | Other Commercial Asset Backed [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	2,821,962	3,119,891
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Assets	122,515	135,215
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Liabilities	114,548	128,988
Variable Interest Entity Nonconsolidated Carrying Amount Derivative Net Assets Or Liabilities	0	0
Global Structured Finance [Member] | Other Debt Obligations [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	3,492,541	3,801,382
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Assets	89,082	97,345
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Liabilities	463,739	599,915
Variable Interest Entity Nonconsolidated Carrying Amount Derivative Net Assets Or Liabilities	15,884	18,176
Global Public Finance [Member]
Variable Interest Entities [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	31,198,824	31,639,004
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Assets	442,871	457,774
Variable Interest Entity Nonconsolidated Carrying Amount Insurance Liabilities	509,380	533,192
Variable Interest Entity Nonconsolidated Carrying Amount Derivative Net Assets Or Liabilities	$ (25,631)	$ (22,135)