Fair Value Measurements - Summary of Changes in Level 3 Fair Value Category (Detail) (USD $) In Thousands, unless otherwise specified	8 Months Ended											4 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended	8 Months Ended	4 Months Ended	12 Months Ended	8 Months Ended	4 Months Ended	12 Months Ended	8 Months Ended	4 Months Ended	12 Months Ended	8 Months Ended	4 Months Ended	12 Months Ended	8 Months Ended	4 Months Ended	12 Months Ended
	Dec. 31, 2013 Successor Ambac [Member] Derivatives by Class [Member]	Dec. 31, 2013 Successor Ambac [Member] Investment by Class [Member]	Dec. 31, 2013 Successor Ambac [Member] Investment by Class [Member] Other Asset Backed Securities [Member]	Dec. 31, 2013 Successor Ambac [Member] Investment by Class [Member] U.S. Agency Obligations [Member]	Dec. 31, 2013 Successor Ambac [Member] Level 3 [Member]	Dec. 31, 2013 Successor Ambac [Member] Level 3 [Member] Investments Contract [Member]	Dec. 31, 2013 Successor Ambac [Member] Level 3 [Member] Loans [Member]	Dec. 31, 2013 Successor Ambac [Member] Level 3 [Member] Long-Term Debt [Member]	Dec. 31, 2013 Successor Ambac [Member] Level 3 [Member] Investments [Member]	Dec. 31, 2013 Successor Ambac [Member] Level 3 [Member] Other Assets [Member]	Dec. 31, 2013 Successor Ambac [Member] Level 3 [Member] Derivatives Assets [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Derivatives by Class [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Derivatives by Class [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Investment by Class [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Investment by Class [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Investment by Class [Member] Other Asset Backed Securities [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Investment by Class [Member] Other Asset Backed Securities [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Investment by Class [Member] U.S. Agency Obligations [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Investment by Class [Member] U.S. Agency Obligations [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Level 3 [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Level 3 [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Level 3 [Member] Investments Contract [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Level 3 [Member] Investments Contract [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Level 3 [Member] Loans [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Level 3 [Member] Loans [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Level 3 [Member] Long-Term Debt [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Level 3 [Member] Long-Term Debt [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Level 3 [Member] Investments [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Level 3 [Member] Investments [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Level 3 [Member] Other Assets [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Level 3 [Member] Other Assets [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Level 3 [Member] Derivatives Assets [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Level 3 [Member] Derivatives Assets [Member]	Dec. 31, 2013 Interest Rate Swaps [Member] Successor Ambac [Member] Derivatives by Class [Member]	Apr. 30, 2013 Interest Rate Swaps [Member] Predecessor Ambac [Member] Derivatives by Class [Member]	Dec. 31, 2012 Interest Rate Swaps [Member] Predecessor Ambac [Member] Derivatives by Class [Member]	Dec. 31, 2013 Credit Derivatives [Member] Successor Ambac [Member] Derivatives by Class [Member]	Apr. 30, 2013 Credit Derivatives [Member] Predecessor Ambac [Member] Derivatives by Class [Member]	Dec. 31, 2012 Credit Derivatives [Member] Predecessor Ambac [Member] Derivatives by Class [Member]	Dec. 31, 2013 Call Options on Long-Term Debt [Member] Successor Ambac [Member] Derivatives by Class [Member]	Apr. 30, 2013 Call Options on Long-Term Debt [Member] Predecessor Ambac [Member] Derivatives by Class [Member]	Dec. 31, 2012 Call Options on Long-Term Debt [Member] Predecessor Ambac [Member] Derivatives by Class [Member]	Dec. 31, 2013 Collateralized Debt Obligations [Member] Successor Ambac [Member] Investment by Class [Member]	Apr. 30, 2013 Collateralized Debt Obligations [Member] Predecessor Ambac [Member] Investment by Class [Member]	Dec. 31, 2012 Collateralized Debt Obligations [Member] Predecessor Ambac [Member] Investment by Class [Member]	Dec. 31, 2013 Corporate Obligations [Member] Successor Ambac [Member] Investment by Class [Member]	Apr. 30, 2013 Corporate Obligations [Member] Predecessor Ambac [Member] Investment by Class [Member]	Dec. 31, 2012 Corporate Obligations [Member] Predecessor Ambac [Member] Investment by Class [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	$ (415,360)	$ 69,412	$ 61,782		$ 15,170,359	$ 2,500,565	$ 14,752,053	$ (1,750,372)	$ 69,412	$ 14,061	$ (415,360)	$ (322,337)	$ (486,775)	$ 60,402	$ 97,522	$ 50,264	$ 75,886		$ 1,224	$ 14,416,488	$ 14,019,216	$ 2,261,294	$ 2,199,338	$ 15,359,073	$ 14,126,994	$ (2,956,501)	$ (1,934,642)	$ 60,402	$ 97,522	$ 14,557	$ 16,779	$ (322,337)	$ (486,775)	$ (137,947)	$ (108,752)	$ (302,177)	$ (277,413)	$ (213,585)	$ (190,653)			$ 6,055	$ 3,949	$ 6,482	$ 12,482	$ 3,681	$ 3,656	$ 7,930
Additions of VIEs consolidated																				(409,300)						(409,300)
Included in earnings	217,666	1,870	1,912	(5)	(417,184)	(178,322)	(455,231)	(2,490)	1,870	(677)	217,666	(88,546)	21,076	(33)	(3)				(2)	1,057,181	721,347	328,768	(41,289)	956,402	952,463	(138,914)	(208,678)	(33)	(3)	(496)	(2,222)	(88,546)	21,076	24,797	(28,162)	(70,415)	192,869	(60,384)	(9,219)			100,710	25	(6)	(5)	(62)	(27)	4
Included in other comprehensive income		7,184	7,315	5	955,046	152,939	873,986	(79,063)	7,184					12,329	7,485	12,117	7,051		(9)	(776,014)	650,373	(89,497)	103,245	(849,833)	637,954	150,987	(98,311)	12,329	7,485														(19)	160	646	(117)	52	(203)
Purchases
Issuances																					(162,460)						(162,460)
Sales		(4,528)	(4,528)		(4,528)				(4,528)
Settlements	10,760	(6,428)	(2,408)	(65)	(42,381)		(219,909)	173,196	(6,428)		10,760	(4,477)	(48,886)	(3,286)	(97,206)	(599)	(85,741)		(749)	(716,488)	(439,649)			(713,589)	(358,338)	4,864	64,781	(3,286)	(97,206)			(4,477)	(48,886)	20,538	(1,033)	71,592	(9,778)	(3,444)	(13,713)			(106,765)	(3,955)	(2,687)	(6,641)			(4,075)
Transfers in Level 3		273		273	(220,649)			(220,922)	273						58,905		53,068				(1,816,216)						(1,875,121)		58,905																			5,837
Transfers out of Level 3					365,046			365,046					192,248		(6,301)				(464)	1,598,492	1,443,877					1,598,492	1,257,930		(6,301)				192,248			192,248												(5,837)
Deconsolidation of VIEs					(1,552,004)		(1,552,004)
Balance, end of period	(186,934)	67,783	64,073	208	14,253,705	2,475,182	13,398,895	(1,514,605)	67,783	13,384	(186,934)	(415,360)	(322,337)	69,412	60,402	61,782	50,264			15,170,359	14,416,488	2,500,565	2,261,294	14,752,053	15,359,073	(1,750,372)	(2,956,501)	69,412	60,402	14,061	14,557	(415,360)	(322,337)	(92,612)	(137,947)	(108,752)	(94,322)	(277,413)	(213,585)					3,949	6,482	3,502	3,681	3,656
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	$ 91,436				$ (545,123)	$ (178,322)	$ (475,152)	$ (2,490)		$ (677)	$ 91,436	$ (92,002)	$ (113,836)							$ 1,053,758	$ 587,983	$ 328,768	$ (41,289)	$ 956,402	$ 952,944	$ (138,914)	$ (208,678)			$ (496)	$ (2,222)	$ (92,002)	$ (113,836)	$ 24,797	$ (28,162)	$ (78,505)	$ 66,639	$ (63,840)	$ (35,331)