Derivative Instruments - Summary of Gross Fair Values of Individual Derivative Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	$ 91,320	$ 77,711
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	348,427	253,898
Successor Ambac [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	141,427	134,587
Gross Amounts of Recognized Liabilities, Derivative Liabilities	398,534	310,774
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	50,107	56,876
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	50,107	56,876
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	91,320	77,711
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	348,427	253,898
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Assets	0	690
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	110,646	42,555
Net Amount, Derivative Assets	91,320	77,021
Net Amount, Derivative Liabilities	237,781	211,343
Successor Ambac [Member] | Variable Interest Entities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities, Derivative Liabilities	1,955,291	1,772,306
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0	0
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,955,291	1,772,306
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	0	0
Net Amount, Derivative Liabilities	1,955,291	1,772,306
Successor Ambac [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	139,266	132,250
Gross Amounts of Recognized Liabilities, Derivative Liabilities	314,515	216,287
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	50,107	56,876
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	50,107	56,876
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	89,159	75,374
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	264,408	159,411
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Assets
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	110,646	42,555
Net Amount, Derivative Assets	89,159	75,374
Net Amount, Derivative Liabilities	153,762	116,856
Successor Ambac [Member] | Interest Rate Swaps [Member] | Variable Interest Entities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities, Derivative Liabilities	1,885,244	1,680,834
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,885,244	1,680,834
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities
Net Amount, Derivative Liabilities	1,885,244	1,680,834
Successor Ambac [Member] | Futures Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	1,109	2,337
Gross Amounts of Recognized Liabilities, Derivative Liabilities	0
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	1,109	2,337
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	0
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Assets		690
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	0
Net Amount, Derivative Assets	1,109	1,647
Net Amount, Derivative Liabilities	0
Successor Ambac [Member] | Credit Derivatives [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	1,052
Gross Amounts of Recognized Liabilities, Derivative Liabilities	83,882	94,322
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	1,052
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	83,882	94,322
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Assets
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities
Net Amount, Derivative Assets	1,052
Net Amount, Derivative Liabilities	83,882	94,322
Successor Ambac [Member] | Other Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities, Derivative Liabilities	137	165
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	137	165
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities
Net Amount, Derivative Liabilities	137	165
Successor Ambac [Member] | Currency Swaps [Member] | Variable Interest Entities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities, Derivative Liabilities	70,047	91,472
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	70,047	91,472
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities
Net Amount, Derivative Liabilities	$ 70,047	$ 91,472