Special Purpose Entities, Including Variable Interest Entities - Summary of Carrying Amount of Assets, Liabilities and Maximum Exposure to Loss of Ambac's Variable Interests in Non-Consolidated Variable Interest Entities (Detail) (Variable Interest Entity [Member], Successor Ambac [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	$ 71,539,440	$ 74,067,088
Insurance Assets	1,709,994	1,728,422
Insurance Liabilities	6,472,925	6,662,385
Derivative Liabilities	74,213	81,432
Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	36,851,335	38,334,230
Insurance Assets	1,180,065	1,196,903
Insurance Liabilities	5,869,929	6,058,046
Derivative Liabilities	46,189	54,320
Global Public Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	34,688,105	35,732,858
Insurance Assets	529,929	531,519
Insurance Liabilities	602,996	604,339
Derivative Liabilities	28,024	27,112
Collateralized Debt Obligations [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	1,806,043	2,092,072
Insurance Assets	2,413	3,867
Insurance Liabilities	5,868	7,119
Derivative Liabilities	7,803	10,092
Residential Mortgage-Backed Securities [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	18,511,853	19,231,335
Insurance Assets	588,700	581,498
Insurance Liabilities	3,797,261	3,890,937
Derivative Liabilities
Other Consumer Asset-Backed [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	5,339,529	5,425,583
Insurance Assets	67,787	68,511
Insurance Liabilities	882,389	992,177
Derivative Liabilities	0	0
Other Commercial Asset-Backed [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	6,836,050	7,237,953
Insurance Assets	408,830	429,559
Insurance Liabilities	537,413	559,600
Derivative Liabilities	34,440	39,916
Other [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	4,357,860	4,347,287
Insurance Assets	112,335	113,468
Insurance Liabilities	646,998	608,213
Derivative Liabilities	$ 3,946	$ 4,312