Derivative Instruments - Summary of Location and Amount of Gains and Losses of Derivative Contracts (Detail) (USD $) In Thousands, unless otherwise specified	2 Months Ended											1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended	1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2013 Successor Ambac [Member]	Jun. 30, 2013 Successor Ambac [Member] Variable Interest Entity [Member]	Jun. 30, 2013 Successor Ambac [Member] Financial Services derivatives products [Member]	Jun. 30, 2013 Successor Ambac [Member] Credit Derivatives [Member] Financial Guarantee [Member] Net change in fair value of credit derivatives [Member]	Jun. 30, 2013 Successor Ambac [Member] Interest Rate Swaps [Member] Income on variable interest entities [Member] Variable Interest Entity [Member]	Jun. 30, 2013 Successor Ambac [Member] Interest Rate Swaps [Member] Financial Services derivatives products [Member] Derivative products [Member]	Jun. 30, 2013 Successor Ambac [Member] Currency Swaps [Member] Income on variable interest entities [Member] Variable Interest Entity [Member]	Jun. 30, 2013 Successor Ambac [Member] Currency Swaps [Member] Financial Services derivatives products [Member] Derivative products [Member]	Jun. 30, 2013 Successor Ambac [Member] Futures contracts [Member] Financial Services derivatives products [Member] Derivative products [Member]	Jun. 30, 2013 Successor Ambac [Member] Other derivatives [Member] Financial Services derivatives products [Member] Derivative products [Member]	Jun. 30, 2013 Successor Ambac [Member] Call options on long-term debt [Member] Other income [Member]	Apr. 30, 2013 Predecessor Ambac [Member]	Jun. 30, 2012 Predecessor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member]	Jun. 30, 2012 Predecessor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Variable Interest Entity [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Variable Interest Entity [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Financial Services derivatives products [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Financial Services derivatives products [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Financial Services derivatives products [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Financial Services derivatives products [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Credit Derivatives [Member] Financial Guarantee [Member] Net change in fair value of credit derivatives [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Credit Derivatives [Member] Financial Guarantee [Member] Net change in fair value of credit derivatives [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Credit Derivatives [Member] Financial Guarantee [Member] Net change in fair value of credit derivatives [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Credit Derivatives [Member] Financial Guarantee [Member] Net change in fair value of credit derivatives [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Interest Rate Swaps [Member] Income on variable interest entities [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Interest Rate Swaps [Member] Income on variable interest entities [Member] Variable Interest Entity [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Interest Rate Swaps [Member] Income on variable interest entities [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Interest Rate Swaps [Member] Income on variable interest entities [Member] Variable Interest Entity [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Interest Rate Swaps [Member] Financial Services derivatives products [Member] Derivative products [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Interest Rate Swaps [Member] Financial Services derivatives products [Member] Derivative products [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Interest Rate Swaps [Member] Financial Services derivatives products [Member] Derivative products [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Interest Rate Swaps [Member] Financial Services derivatives products [Member] Derivative products [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Currency Swaps [Member] Income on variable interest entities [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Currency Swaps [Member] Income on variable interest entities [Member] Variable Interest Entity [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Currency Swaps [Member] Income on variable interest entities [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Currency Swaps [Member] Income on variable interest entities [Member] Variable Interest Entity [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Currency Swaps [Member] Financial Services derivatives products [Member] Derivative products [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Currency Swaps [Member] Financial Services derivatives products [Member] Derivative products [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Futures contracts [Member] Financial Services derivatives products [Member] Derivative products [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Futures contracts [Member] Financial Services derivatives products [Member] Derivative products [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Futures contracts [Member] Financial Services derivatives products [Member] Derivative products [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Futures contracts [Member] Financial Services derivatives products [Member] Derivative products [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Other derivatives [Member] Financial Services derivatives products [Member] Derivative products [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Other derivatives [Member] Financial Services derivatives products [Member] Derivative products [Member]	Apr. 30, 2013 Predecessor Ambac [Member] Other derivatives [Member] Financial Services derivatives products [Member] Derivative products [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Other derivatives [Member] Financial Services derivatives products [Member] Derivative products [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Call options on long-term debt [Member] Other income [Member]	Jun. 30, 2012 Predecessor Ambac [Member] Call options on long-term debt [Member] Other income [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total				$ 51,220	$ 437,624	$ 74,169	$ (1,890)		$ 9,831	$ (287)														$ (73,171)	$ (7,415)	$ (60,384)	$ (14,637)	$ (103,072)	$ (48,478)	$ (203,620)	$ 45,237	$ (29,600)	$ (108,175)	$ (30,622)	$ (65,990)	$ (4,820)	$ (10,787)	$ (116)	$ (21,994)	$ 81	$ 237	$ (3,588)	$ (16,070)	$ (3,133)	$ (11,762)	$ 22	$ 73	$ 20	$ 381	$ 39,030	$ 100,710
Derivative, gain (loss) on derivative, net, Total	$ 570,667	$ 435,734	$ 83,713									$ (214,229)	$ (151,741)	$ (297,855)	$ 32,182	$ (107,892)	$ (59,265)	$ (203,736)	$ 23,243	$ (33,166)	$ (124,091)	$ (33,735)	$ (77,134)