Derivative Instruments - Summary of Gross Principal Notional Outstanding for CDS Contracts (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Ambac Rating
Notional outstanding	$ 5,207,364	$ 11,281,777
Predecessor Ambac [Member]
Ambac Rating
Notional outstanding		11,281,777
Successor Ambac [Member]
Ambac Rating
Notional outstanding	5,207,364
Other Derivatives [Member] | Predecessor Ambac [Member]
Ambac Rating
Notional outstanding		11,281,777
Other Derivatives [Member] | Predecessor Ambac [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding		678,483
Other Derivatives [Member] | Predecessor Ambac [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding		5,955,118
Other Derivatives [Member] | Predecessor Ambac [Member] | A Rating [Member]
Ambac Rating
Notional outstanding		3,684,193
Other Derivatives [Member] | Predecessor Ambac [Member] | BBB Rating [Member]
Ambac Rating
Notional outstanding		672,293
Other Derivatives [Member] | Predecessor Ambac [Member] | Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding		291,690
Other Derivatives [Member] | Successor Ambac [Member]
Ambac Rating
Notional outstanding	5,207,364
Other Derivatives [Member] | Successor Ambac [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding	672,459
Other Derivatives [Member] | Successor Ambac [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding	1,495,605
Other Derivatives [Member] | Successor Ambac [Member] | A Rating [Member]
Ambac Rating
Notional outstanding	1,901,712
Other Derivatives [Member] | Successor Ambac [Member] | BBB Rating [Member]
Ambac Rating
Notional outstanding	856,041
Other Derivatives [Member] | Successor Ambac [Member] | Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding	281,547
CLO [Member] | Predecessor Ambac [Member]
Ambac Rating
Notional outstanding		6,155,767
CLO [Member] | Successor Ambac [Member]
Ambac Rating
Notional outstanding	1,609,378
CLO [Member] | Other Derivatives [Member] | Predecessor Ambac [Member]
Ambac Rating
Notional outstanding		6,155,767
CLO [Member] | Other Derivatives [Member] | Predecessor Ambac [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding		166,200
CLO [Member] | Other Derivatives [Member] | Predecessor Ambac [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding		4,676,362
CLO [Member] | Other Derivatives [Member] | Predecessor Ambac [Member] | A Rating [Member]
Ambac Rating
Notional outstanding		1,313,205
CLO [Member] | Other Derivatives [Member] | Predecessor Ambac [Member] | BBB Rating [Member]
Ambac Rating
Notional outstanding
CLO [Member] | Other Derivatives [Member] | Predecessor Ambac [Member] | Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding
CLO [Member] | Other Derivatives [Member] | Successor Ambac [Member]
Ambac Rating
Notional outstanding	1,609,378
CLO [Member] | Other Derivatives [Member] | Successor Ambac [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding	193,286
CLO [Member] | Other Derivatives [Member] | Successor Ambac [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding	1,289,541
CLO [Member] | Other Derivatives [Member] | Successor Ambac [Member] | A Rating [Member]
Ambac Rating
Notional outstanding	126,551
Other [Member] | Predecessor Ambac [Member]
Ambac Rating
Notional outstanding		5,126,010
Other [Member] | Successor Ambac [Member]
Ambac Rating
Notional outstanding	3,597,986
Other [Member] | Other Derivatives [Member] | Predecessor Ambac [Member]
Ambac Rating
Notional outstanding		5,126,010
Other [Member] | Other Derivatives [Member] | Predecessor Ambac [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding		512,283
Other [Member] | Other Derivatives [Member] | Predecessor Ambac [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding		1,278,756
Other [Member] | Other Derivatives [Member] | Predecessor Ambac [Member] | A Rating [Member]
Ambac Rating
Notional outstanding		2,370,988
Other [Member] | Other Derivatives [Member] | Predecessor Ambac [Member] | BBB Rating [Member]
Ambac Rating
Notional outstanding		672,293
Other [Member] | Other Derivatives [Member] | Predecessor Ambac [Member] | Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding		291,690
Other [Member] | Other Derivatives [Member] | Successor Ambac [Member]
Ambac Rating
Notional outstanding	3,597,986
Other [Member] | Other Derivatives [Member] | Successor Ambac [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding	479,173
Other [Member] | Other Derivatives [Member] | Successor Ambac [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding	206,064
Other [Member] | Other Derivatives [Member] | Successor Ambac [Member] | A Rating [Member]
Ambac Rating
Notional outstanding	1,775,161
Other [Member] | Other Derivatives [Member] | Successor Ambac [Member] | BBB Rating [Member]
Ambac Rating
Notional outstanding	856,041
Other [Member] | Other Derivatives [Member] | Successor Ambac [Member] | Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding	$ 281,547