Segment Information - Summary of Financial Information by Reportable Segment (Detail) (USD $) In Thousands, unless otherwise specified			3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Successor Ambac [Member]	Mar. 31, 2014 Successor Ambac [Member] Unaffiliated Customers [Member]	Mar. 31, 2013 Predecessor Ambac [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Unaffiliated Customers [Member]	Mar. 31, 2014 Operating Segments [Member] Successor Ambac [Member] Financial Guarantee [Member]	Mar. 31, 2014 Operating Segments [Member] Successor Ambac [Member] Financial Guarantee [Member] Unaffiliated Customers [Member]	Mar. 31, 2014 Operating Segments [Member] Successor Ambac [Member] Financial Guarantee [Member] Inter-Segment [Member]	Mar. 31, 2014 Operating Segments [Member] Successor Ambac [Member] Financial Services [Member]	Mar. 31, 2014 Operating Segments [Member] Successor Ambac [Member] Financial Services [Member] Unaffiliated Customers [Member]	Mar. 31, 2014 Operating Segments [Member] Successor Ambac [Member] Financial Services [Member] Inter-Segment [Member]	Mar. 31, 2013 Operating Segments [Member] Predecessor Ambac [Member] Financial Guarantee [Member]	Mar. 31, 2013 Operating Segments [Member] Predecessor Ambac [Member] Financial Guarantee [Member] Unaffiliated Customers [Member]	Mar. 31, 2013 Operating Segments [Member] Predecessor Ambac [Member] Financial Guarantee [Member] Inter-Segment [Member]	Mar. 31, 2013 Operating Segments [Member] Predecessor Ambac [Member] Financial Services [Member]	Mar. 31, 2013 Operating Segments [Member] Predecessor Ambac [Member] Financial Services [Member] Unaffiliated Customers [Member]	Mar. 31, 2013 Operating Segments [Member] Predecessor Ambac [Member] Financial Services [Member] Inter-Segment [Member]	Mar. 31, 2014 Corporate and Other [Member] Successor Ambac [Member]	Mar. 31, 2014 Corporate and Other [Member] Successor Ambac [Member] Unaffiliated Customers [Member]	Mar. 31, 2014 Corporate and Other [Member] Successor Ambac [Member] Inter-Segment [Member]	Mar. 31, 2013 Corporate and Other [Member] Predecessor Ambac [Member]	Mar. 31, 2013 Corporate and Other [Member] Predecessor Ambac [Member] Unaffiliated Customers [Member]	Mar. 31, 2013 Corporate and Other [Member] Predecessor Ambac [Member] Inter-Segment [Member]	Mar. 31, 2014 Inter-segment Eliminations [Member] Successor Ambac [Member]	Mar. 31, 2014 Inter-segment Eliminations [Member] Successor Ambac [Member] Inter-Segment [Member]	Mar. 31, 2013 Inter-segment Eliminations [Member] Predecessor Ambac [Member]	Mar. 31, 2013 Inter-segment Eliminations [Member] Predecessor Ambac [Member] Inter-Segment [Member]
Revenues:
Total revenues before expenses and reorganization items			$ 109,138	$ 109,138	$ 290,872	$ 290,872	$ 162,928	$ 162,553	$ 375	$ (53,513)	$ (53,438)	$ (75)	$ 250,964	$ 250,238	$ 726	$ 39,921	$ 40,605	$ (684)	$ 8,658	$ 23	$ 8,635	$ 29	$ 29		$ (8,935)	$ (8,935)	$ (42)	$ (42)
Pre-tax income (loss) from continuing operations:
Pre-tax income (loss) from continuing operations			159,298	159,298	282,909	282,909	207,104	216,261	(9,157)	(54,983)	(54,529)	(454)	246,628	246,700	(72)	37,998	38,847	(849)	7,177	(2,434)	9,611	(1,717)	(2,638)	921
Total assets	27,114,248	27,092,477	27,114,248		26,154,094		26,535,119			534,256			25,563,432			558,593			44,873			32,069
Net investment income			70,801		84,514		70,384			394			83,274			1,211			23			29
Insurance intangible amortization			31,714		0		31,714
Interest expense			32,328		23,165		31,881			447			22,176			989
Reorganization items			$ 23		$ 2,059														$ 23			$ 2,059