Segment Information - Schedule of Gross Premiums Written, Net Premiums Earned and Net Change in Fair Value of Credit Derivatives (Detail) (USD $) In Thousands, unless otherwise specified	2 Months Ended	3 Months Ended	6 Months Ended	2 Months Ended	3 Months Ended	6 Months Ended	2 Months Ended	3 Months Ended	6 Months Ended	2 Months Ended	3 Months Ended	6 Months Ended	1 Months Ended	4 Months Ended	1 Months Ended	4 Months Ended	1 Months Ended	4 Months Ended	1 Months Ended	4 Months Ended
	Jun. 30, 2013 Successor Ambac [Member]	Jun. 30, 2014 Successor Ambac [Member]	Jun. 30, 2014 Successor Ambac [Member]	Jun. 30, 2013 Successor Ambac [Member] Reportable Geographical Components [Member] United States [Member]	Jun. 30, 2014 Successor Ambac [Member] Reportable Geographical Components [Member] United States [Member]	Jun. 30, 2014 Successor Ambac [Member] Reportable Geographical Components [Member] United States [Member]	Jun. 30, 2013 Successor Ambac [Member] Reportable Geographical Components [Member] United Kingdom [Member]	Jun. 30, 2014 Successor Ambac [Member] Reportable Geographical Components [Member] United Kingdom [Member]	Jun. 30, 2014 Successor Ambac [Member] Reportable Geographical Components [Member] United Kingdom [Member]	Jun. 30, 2013 Successor Ambac [Member] Reportable Geographical Components [Member] Other International [Member]	Jun. 30, 2014 Successor Ambac [Member] Reportable Geographical Components [Member] Other International [Member]	Jun. 30, 2014 Successor Ambac [Member] Reportable Geographical Components [Member] Other International [Member]	Apr. 30, 2013 Predecessor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Reportable Geographical Components [Member] United States [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Reportable Geographical Components [Member] United States [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Reportable Geographical Components [Member] United Kingdom [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Reportable Geographical Components [Member] United Kingdom [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Reportable Geographical Components [Member] Other International [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Reportable Geographical Components [Member] Other International [Member]
Segment Reporting Information [Line Items]
Gross Premiums Written	$ (34,081)	$ (45,486)	$ (51,252)	$ (24,493)	$ (28,211)	$ (28,909)	$ (1,917)	$ 3,003	$ (3,163)	$ (7,671)	$ (20,278)	$ (19,180)	$ (10,595)	$ (14,125)	$ (7,386)	$ (16,102)	$ 2,167	$ 10,673	$ (5,376)	$ (8,696)
Net premiums earned	58,039	65,013	147,560	46,340	39,833	96,591	8,840	20,808	41,443	2,859	4,372	9,526	29,744	130,000	23,537	104,594	4,317	18,071	1,890	7,335
Net Change In Fair Value Of Credit Derivatives	$ 51,220	$ (1,219)	$ 6,163	$ 14,948	$ (559)	$ 6,022	$ 2,113	$ 0	$ 0	$ 34,159	$ (660)	$ 141	$ (73,171)	$ (60,384)	$ (47,664)	$ (31,134)	$ (3,686)	$ (5,861)	$ (21,821)	$ (23,389)