Derivative Instruments - Summary of Net Par Outstanding for CDS Contracts (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Ambac Rating
Notional outstanding	$ 5,861,060	$ 11,281,777
Predecessor Ambac [Member]
Ambac Rating
Notional outstanding		11,281,777
Predecessor Ambac [Member] \| AAA Rating [Member]
Ambac Rating
Notional outstanding		678,483
Predecessor Ambac [Member] \| AA Rating [Member]
Ambac Rating
Notional outstanding		5,955,118
Predecessor Ambac [Member] \| A Rating [Member]
Ambac Rating
Notional outstanding		3,684,193
Predecessor Ambac [Member] \| BBB Rating [Member]
Ambac Rating
Notional outstanding		672,293
Predecessor Ambac [Member] \| Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding		291,690
Successor Ambac [Member]
Ambac Rating
Notional outstanding	5,861,060
Successor Ambac [Member] \| AAA Rating [Member]
Ambac Rating
Notional outstanding	465,858
Successor Ambac [Member] \| AA Rating [Member]
Ambac Rating
Notional outstanding	2,305,454
Successor Ambac [Member] \| A Rating [Member]
Ambac Rating
Notional outstanding	1,927,429
Successor Ambac [Member] \| BBB Rating [Member]
Ambac Rating
Notional outstanding	882,332
Successor Ambac [Member] \| Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding	279,987
CLO [Member] \| Predecessor Ambac [Member]
Ambac Rating
Notional outstanding		6,155,767
CLO [Member] \| Predecessor Ambac [Member] \| AAA Rating [Member]
Ambac Rating
Notional outstanding		166,200
CLO [Member] \| Predecessor Ambac [Member] \| AA Rating [Member]
Ambac Rating
Notional outstanding		4,676,362
CLO [Member] \| Predecessor Ambac [Member] \| A Rating [Member]
Ambac Rating
Notional outstanding		1,313,205
CLO [Member] \| Predecessor Ambac [Member] \| BBB Rating [Member]
Ambac Rating
Notional outstanding
CLO [Member] \| Predecessor Ambac [Member] \| Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding
CLO [Member] \| Successor Ambac [Member]
Ambac Rating
Notional outstanding	1,750,217
CLO [Member] \| Successor Ambac [Member] \| AAA Rating [Member]
Ambac Rating
Notional outstanding	13,346
CLO [Member] \| Successor Ambac [Member] \| AA Rating [Member]
Ambac Rating
Notional outstanding	1,568,030
CLO [Member] \| Successor Ambac [Member] \| A Rating [Member]
Ambac Rating
Notional outstanding	168,841
Other [Member] \| Predecessor Ambac [Member]
Ambac Rating
Notional outstanding		5,126,010
Other [Member] \| Predecessor Ambac [Member] \| AAA Rating [Member]
Ambac Rating
Notional outstanding		512,283
Other [Member] \| Predecessor Ambac [Member] \| AA Rating [Member]
Ambac Rating
Notional outstanding		1,278,756
Other [Member] \| Predecessor Ambac [Member] \| A Rating [Member]
Ambac Rating
Notional outstanding		2,370,988
Other [Member] \| Predecessor Ambac [Member] \| BBB Rating [Member]
Ambac Rating
Notional outstanding		672,293
Other [Member] \| Predecessor Ambac [Member] \| Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding		291,690
Other [Member] \| Successor Ambac [Member]
Ambac Rating
Notional outstanding	4,110,843
Other [Member] \| Successor Ambac [Member] \| AAA Rating [Member]
Ambac Rating
Notional outstanding	452,512
Other [Member] \| Successor Ambac [Member] \| AA Rating [Member]
Ambac Rating
Notional outstanding	737,424
Other [Member] \| Successor Ambac [Member] \| A Rating [Member]
Ambac Rating
Notional outstanding	1,758,588
Other [Member] \| Successor Ambac [Member] \| BBB Rating [Member]
Ambac Rating
Notional outstanding	882,332
Other [Member] \| Successor Ambac [Member] \| Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding	$ 279,987