Fresh Start Financial Statement Reporting - Summary of Reorganization Items in Consolidated Statements of Total Comprehensive Income (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]
Fresh-Start Adjustment [Line Items]
U.S. Trustee fees	$ 13	$ 13	$ 13	$ 23	$ 39
Professional fees	(9)	415	1,239	4,483	4,441
Gain on settlement of liabilities subject to compromise				(1,521,435)
Fresh start reporting adjustments				(1,228,251)
Total reorganization items	$ 4	$ 428	$ 1,252	$ (2,745,180)	$ 4,480