Fair Value Measurements - Summary of Information about Described Model Inputs Used to Determine Fair Value of Each Class of Credit Derivatives (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items]
Notional outstanding	$ 5,861,060	$ 11,281,777
Successor Ambac [Member]
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items]
Notional outstanding	5,861,060
Predecessor Ambac [Member]
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items]
Notional outstanding		11,281,777
CLO [Member] | Successor Ambac [Member]
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items]
Notional outstanding	1,750,217
Weighted average reference obligation price	$ 97.7
Weighted average life (WAL) in years	2 years 6 months
Weighted average credit rating	AA
Weighted average relative change ratio	35.30%
CVA percentage	15.10%
Fair value of derivative liabilities	(11,996)
CLO [Member] | Predecessor Ambac [Member]
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items]
Notional outstanding		6,155,767
Weighted average reference obligation price		$ 96.5
Weighted average life (WAL) in years		2 years 2 months 12 days
Weighted average credit rating		AA-
Weighted average relative change ratio		34.40%
CVA percentage		55.00%
Fair value of derivative liabilities		(34,645)
Other [Member] | Successor Ambac [Member]
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items]
Notional outstanding	2,940,586
Weighted average reference obligation price	$ 88.5
Weighted average life (WAL) in years	4 years 3 months 18 days
Weighted average credit rating	A-
Weighted average relative change ratio	37.40%
CVA percentage	31.20%
Fair value of derivative liabilities	(134,161)
Other [Member] | Predecessor Ambac [Member]
Schedule Of Information About Described Model Inputs Used To Determine Fair Value Of Each Class Of Credit Derivative [Line Items]
Notional outstanding		3,701,387
Weighted average reference obligation price		$ 86.9
Weighted average life (WAL) in years		4 years 2 months 12 days
Weighted average credit rating		A
Weighted average relative change ratio		38.20%
CVA percentage		55.00%
Fair value of derivative liabilities		$ (116,086)