Derivative Instruments - Summary of Gross Principal Notional Outstanding for CDS Contracts (Detail) - Successor [Member] - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Ambac Rating
Notional outstanding	$ 455,792	$ 737,380
Other Derivatives [Member]
Ambac Rating
Notional outstanding	455,792	737,380
Other Derivatives [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding	0	0
Other Derivatives [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding	240,850	315,201
Other Derivatives [Member] | A Rating [Member]
Ambac Rating
Notional outstanding	0	227,146
Other Derivatives [Member] | BBB Rating [Member]
Ambac Rating
Notional outstanding	142,750	127,250
Other Derivatives [Member] | Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding	$ 72,192	$ 67,783