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	3 Months Ended	4 Months Ended	9 Months Ended
	Sep. 30, 2013 Successor Ambac [Member]	Sep. 30, 2013 Successor Ambac [Member]	Sep. 30, 2012 Predecessor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member]	Sep. 30, 2012 Predecessor Ambac [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Written	$ (34,380)	$ (68,461)	$ (55,310)	$ (14,125)	$ (175,777)
Assumed Reinsurance Premiums Written
Ceded Reinsurance Premiums Written	(4,017)	(7,055)	(2,082)	(1,098)	(18,055)
Premiums written, net of reinsurance	(30,363)	(61,406)	(53,228)	(13,027)	(157,722)
Direct Premiums Earned	73,997	136,029	117,864	138,468	323,658
Assumed Reinsurance Premiums Earned	24	40	25	32	118
Ceded Reinsurance Premiums Earned	3,072	7,081	4,815	8,500	12,710
Reinsurance on premiums earned, Net	$ 70,949	$ 128,988	$ 113,074	$ 130,000	$ 311,066