Financial Guarantee Insurance Contracts - Effect of Reinsurance on Premiums Written and Earned (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		5 Months Ended	9 Months Ended	4 Months Ended
	Sep. 30, 2014 Successor Ambac [Member]	Sep. 30, 2013 Successor Ambac [Member]	Sep. 30, 2013 Successor Ambac [Member]	Sep. 30, 2014 Successor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Written	$ (13,700)	$ (34,380)	$ (68,461)	$ (64,952)	$ (14,125)
Assumed Reinsurance Premiums Written	0	0	0	0	0
Ceded Reinsurance Premiums Written	(2,805)	(4,017)	(7,055)	(7,316)	(1,098)
Premiums written, net of reinsurance	(10,895)	(30,363)	(61,406)	(57,636)	(13,027)
Direct Premiums Earned	68,685	73,997	136,029	222,894	138,468
Assumed Reinsurance Premiums Earned	23	24	40	114	32
Ceded Reinsurance Premiums Earned	3,877	3,072	7,081	10,617	8,500
Reinsurance on premiums earned, Net	$ 64,831	$ 70,949	$ 128,988	$ 212,391	$ 130,000