Derivative Instruments - Summary of Location and Amount of Gains and Losses of Derivative Contracts (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	8 Months Ended	4 Months Ended	12 Months Ended	8 Months Ended		4 Months Ended	12 Months Ended	4 Months Ended	12 Months Ended	8 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
	Dec. 31, 2013 Successor Ambac [Member]	Dec. 31, 2013 Successor Ambac [Member] Variable Interest Entity [Member]	Dec. 31, 2013 Successor Ambac [Member] Financial Services Derivatives Products [Member]	Apr. 30, 2013 Predecessor Ambac [Member]	Dec. 31, 2012 Predecessor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Variable Interest Entity [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Variable Interest Entity [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Financial Services Derivatives Products [Member]	Dec. 31, 2012 Predecessor Ambac [Member] Financial Services Derivatives Products [Member]	Dec. 31, 2013 Credit Derivatives [Member] Successor Ambac [Member] Financial Guarantee [Member] Net Change in Fair Value of Credit Derivatives [Member]	Apr. 30, 2013 Credit Derivatives [Member] Predecessor Ambac [Member] Financial Guarantee [Member] Net Change in Fair Value of Credit Derivatives [Member]	Dec. 31, 2012 Credit Derivatives [Member] Predecessor Ambac [Member] Financial Guarantee [Member] Net Change in Fair Value of Credit Derivatives [Member]	Dec. 31, 2013 Interest Rate Swaps [Member] Successor Ambac [Member] (Loss) Income on Variable Interest Entities [Member] Variable Interest Entity [Member]	Dec. 31, 2013 Interest Rate Swaps [Member] Successor Ambac [Member] Financial Services Derivatives Products [Member] Derivative Products [Member]	Apr. 30, 2013 Interest Rate Swaps [Member] Predecessor Ambac [Member] (Loss) Income on Variable Interest Entities [Member] Variable Interest Entity [Member]	Dec. 31, 2012 Interest Rate Swaps [Member] Predecessor Ambac [Member] (Loss) Income on Variable Interest Entities [Member] Variable Interest Entity [Member]	Apr. 30, 2013 Interest Rate Swaps [Member] Predecessor Ambac [Member] Financial Services Derivatives Products [Member] Derivative Products [Member]	Dec. 31, 2012 Interest Rate Swaps [Member] Predecessor Ambac [Member] Financial Services Derivatives Products [Member] Derivative Products [Member]	Dec. 31, 2013 Currency Swaps [Member] Successor Ambac [Member] (Loss) Income on Variable Interest Entities [Member] Variable Interest Entity [Member]	Dec. 31, 2013 Currency Swaps [Member] Successor Ambac [Member] Financial Services Derivatives Products [Member] Derivative Products [Member]	Apr. 30, 2013 Currency Swaps [Member] Predecessor Ambac [Member] (Loss) Income on Variable Interest Entities [Member] Variable Interest Entity [Member]	Dec. 31, 2012 Currency Swaps [Member] Predecessor Ambac [Member] (Loss) Income on Variable Interest Entities [Member] Variable Interest Entity [Member]	Apr. 30, 2013 Currency Swaps [Member] Predecessor Ambac [Member] Financial Services Derivatives Products [Member] Derivative Products [Member]	Dec. 31, 2012 Currency Swaps [Member] Predecessor Ambac [Member] Financial Services Derivatives Products [Member] Derivative Products [Member]	Dec. 31, 2013 Futures Contracts [Member] Successor Ambac [Member] Financial Services Derivatives Products [Member] Derivative Products [Member]	Apr. 30, 2013 Futures Contracts [Member] Predecessor Ambac [Member] Financial Services Derivatives Products [Member] Derivative Products [Member]	Dec. 31, 2012 Futures Contracts [Member] Predecessor Ambac [Member] Financial Services Derivatives Products [Member] Derivative Products [Member]	Dec. 31, 2013 Other Derivatives [Member] Successor Ambac [Member] Financial Services Derivatives Products [Member] Derivative Products [Member]	Apr. 30, 2013 Other Derivatives [Member] Predecessor Ambac [Member] Financial Services Derivatives Products [Member] Derivative Products [Member]	Dec. 31, 2012 Other Derivatives [Member] Predecessor Ambac [Member] Financial Services Derivatives Products [Member] Derivative Products [Member]	Dec. 31, 2013 Call Options on Long-Term Debt [Member] Successor Ambac [Member] Other Income [Member]	Apr. 30, 2013 Call Options on Long-Term Debt [Member] Predecessor Ambac [Member] Other Income [Member]	Dec. 31, 2012 Call Options on Long-Term Debt [Member] Predecessor Ambac [Member] Other Income [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	$ 802,462	$ 494,822	$ 114,771	$ (297,855)	$ (168,242)	$ (203,736)	$ (134,729)	$ (33,735)	$ (125,004)	$ 192,869	$ (60,384)	$ (9,219)	$ 495,712	$ 104,114	$ (203,620)	$ (107,341)	$ (30,622)	$ (111,396)	$ (890)		$ (116)	$ (27,388)		$ 807	$ 10,925	$ (3,133)	$ (14,864)	$ (268)	$ 20	$ 449			$ 100,710