Fair Value Measurements - Summary of Changes in Level 3 Fair Value Category (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 Successor Ambac [Member] Investment by Class [Member]	Mar. 31, 2014 Successor Ambac [Member] Derivatives by Class [Member]	Mar. 31, 2014 Successor Ambac [Member] Asset-backed Securities [Member] Investment by Class [Member]	Mar. 31, 2014 Successor Ambac [Member] U.S. Agency Obligations [Member] Investment by Class [Member]	Mar. 31, 2014 Successor Ambac [Member] Collateralized Debt Obligations [Member] Investment by Class [Member]	Mar. 31, 2014 Successor Ambac [Member] Corporate Obligations [Member] Investment by Class [Member]	Mar. 31, 2014 Successor Ambac [Member] Interest Rate Swaps [Member] Derivatives by Class [Member]	Mar. 31, 2014 Successor Ambac [Member] Credit Derivatives [Member] Derivatives by Class [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Investment by Class [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Derivatives by Class [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Asset-backed Securities [Member] Investment by Class [Member]	Mar. 31, 2013 Predecessor Ambac [Member] U.S. Agency Obligations [Member] Investment by Class [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Collateralized Debt Obligations [Member] Investment by Class [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Corporate Obligations [Member] Investment by Class [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Interest Rate Swaps [Member] Derivatives by Class [Member]	Mar. 31, 2013 Predecessor Ambac [Member] Credit Derivatives [Member] Derivatives by Class [Member]	Mar. 31, 2014 Level 3 [Member] Successor Ambac [Member]	Mar. 31, 2014 Level 3 [Member] Successor Ambac [Member] Investments Contract [Member]	Mar. 31, 2014 Level 3 [Member] Successor Ambac [Member] Loans [Member]	Mar. 31, 2014 Level 3 [Member] Successor Ambac [Member] Long-Term Debt [Member]	Mar. 31, 2014 Level 3 [Member] Successor Ambac [Member] Investments [Member]	Mar. 31, 2014 Level 3 [Member] Successor Ambac [Member] Other Assets [Member]	Mar. 31, 2014 Level 3 [Member] Successor Ambac [Member] Derivative Financial Instruments, Liabilities [Member]	Mar. 31, 2013 Level 3 [Member] Predecessor Ambac [Member]	Mar. 31, 2013 Level 3 [Member] Predecessor Ambac [Member] Investments Contract [Member]	Mar. 31, 2013 Level 3 [Member] Predecessor Ambac [Member] Loans [Member]	Mar. 31, 2013 Level 3 [Member] Predecessor Ambac [Member] Long-Term Debt [Member]	Mar. 31, 2013 Level 3 [Member] Predecessor Ambac [Member] Investments [Member]	Mar. 31, 2013 Level 3 [Member] Predecessor Ambac [Member] Other Assets [Member]	Mar. 31, 2013 Level 3 [Member] Predecessor Ambac [Member] Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 67,783	$ (186,934)	$ 64,073	$ 208		$ 3,502	$ (92,612)	$ (94,322)	$ 60,402	$ (322,337)	$ 50,264		$ 6,482	$ 3,656	$ (108,752)	$ (213,585)	$ 14,253,705	$ 2,475,182	$ 13,398,895	$ (1,514,605)	$ 67,783	$ 13,384	$ (186,934)	$ 14,416,488	$ 2,261,294	$ 15,359,073	$ (2,956,501)	$ 60,402	$ 14,557	$ (322,337)
Additions of VIEs consolidated
Included in earnings	419	(14,249)	443			(24)	(21,631)	7,382	(23)	(3,162)			(3)	(20)	(15,949)	12,787	172,538	55,745	321,847	(190,962)	419	(262)	(14,249)	566,845	297,294	400,456	(127,393)	(23)	(327)	(3,162)
Included in other comprehensive income	(217)		(295)			78			698		569		113	16			86,799	15,835	79,802	(8,621)	(217)			(904,833)	(143,981)	(955,455)	193,905	698
Purchases																	70,000		70,000
Issuances
Sales
Settlements	(854)	(1,299)	(854)				(524)	(775)	(3,286)	(3,190)	(599)		(2,687)		(681)	(2,509)	(173,451)		(601,092)	429,794	(854)		(1,299)	(688,875)		(687,263)	4,864	(3,286)		(3,190)
Transfers in Level 3																	0				0			0			0
Transfers out of Level 3	(208)			(208)													(208)				(208)			974,536			974,536
Deconsolidation of VIEs
Balance, end of period	66,923	(202,482)	63,367			3,556	(114,767)	(87,715)	57,791	(328,689)	50,234	0	3,905	3,652	(125,382)	(203,307)	14,409,383	2,546,762	13,269,452	(1,284,394)	66,923	13,122	(202,482)	14,364,161	2,414,607	14,116,811	(1,910,589)	57,791	14,230	(328,689)
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		$ (15,024)					$ (21,631)	$ 6,607		$ (5,684)					$ (15,949)	$ 10,265	$ 169,349	$ 55,745	$ 316,714	$ (187,824)		$ (262)	$ (15,024)	$ 564,346	$ 297,294	$ 400,456	$ (127,393)		$ (327)	$ (5,684)