Derivative Instruments - Summary of Location and Amount of Gains and Losses of Derivative Contracts (Detail) (Successor Ambac [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		4 Months Ended	5 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Apr. 30, 2013	Sep. 30, 2013	Sep. 30, 2014
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	$ (36,101)	$ (13,855)	$ (297,855)	$ 556,812	$ (286,918)
Variable Interest Entity [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	(27,832)	(57,421)	(203,736)	378,313	(182,986)
Financial Services Derivatives Products [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	(15,685)	12,372	(33,735)	96,085	(117,511)
Credit Derivatives [Member] | Financial Guarantee [Member] | Net Change in Fair Value of Credit Derivatives [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	7,416	31,194	(60,384)	82,414	13,579
Interest Rate Swaps [Member] | Income on Variable Interest Entities [Member] | Variable Interest Entity [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	(44,846)	(63,421)	(203,620)	374,203	(204,411)
Interest Rate Swaps [Member] | Financial Services Derivatives Products [Member] | Derivative Products [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	(15,634)	13,299	(30,622)	87,468	(113,028)
Currency Swaps [Member] | Income on Variable Interest Entities [Member] | Variable Interest Entity [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	17,014	6,000	(116)	4,110	21,425
Futures Contracts [Member] | Financial Services Derivatives Products [Member] | Derivative Products [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	(47)	(961)	(3,133)	8,870	(4,516)
Other Contracts [Member] | Financial Services Derivatives Products [Member] | Derivative Products [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	$ (4)	$ 34	$ 20	$ (253)	$ 33