Derivative Instruments - Summary of Gross Principal Notional Outstanding for CDS Contracts (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Ambac Rating
Notional outstanding	$ 1,529,759	$ 2,776,103
Successor [Member]
Ambac Rating
Notional outstanding	1,529,759	2,776,103
Other Derivatives [Member] | Successor [Member]
Ambac Rating
Notional outstanding	1,529,759	2,776,103
Other Derivatives [Member] | Successor [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding	0	24,034
Other Derivatives [Member] | Successor [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding	767,603	1,412,096
Other Derivatives [Member] | Successor [Member] | A Rating [Member]
Ambac Rating
Notional outstanding	43,160	235,917
Other Derivatives [Member] | Successor [Member] | BBB Rating [Member]
Ambac Rating
Notional outstanding	448,249	826,175
Other Derivatives [Member] | Successor [Member] | Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding	270,747	277,881
CLO [Member] | Successor [Member]
Ambac Rating
Notional outstanding	549,923	1,337,737
CLO [Member] | Other Derivatives [Member] | Successor [Member]
Ambac Rating
Notional outstanding	549,923	1,337,737
CLO [Member] | Other Derivatives [Member] | Successor [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding	0	0
CLO [Member] | Other Derivatives [Member] | Successor [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding	549,923	1,209,071
CLO [Member] | Other Derivatives [Member] | Successor [Member] | A Rating [Member] [Member]
Ambac Rating
Notional outstanding	0	128,666
Other [Member] | Successor [Member]
Ambac Rating
Notional outstanding	979,836	1,438,366
Other [Member] | Other Derivatives [Member] | Successor [Member]
Ambac Rating
Notional outstanding	979,836	1,438,366
Other [Member] | Other Derivatives [Member] | Successor [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding	0	24,034
Other [Member] | Other Derivatives [Member] | Successor [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding	217,680	203,025
Other [Member] | Other Derivatives [Member] | Successor [Member] | A Rating [Member]
Ambac Rating
Notional outstanding	43,160	107,251
Other [Member] | Other Derivatives [Member] | Successor [Member] | BBB Rating [Member]
Ambac Rating
Notional outstanding	448,249	826,175
Other [Member] | Other Derivatives [Member] | Successor [Member] | Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding	$ 270,747	$ 277,881