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	Sep. 30, 2014	Dec. 31, 2013
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	$ 65,202,980	$ 74,067,088
Insurance Assets	1,558,712	1,728,422
Insurance Liabilities	6,469,223	6,662,385
Derivative Liabilities	70,561	81,432
Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	32,731,907	38,334,230
Insurance Assets	1,092,789	1,196,903
Insurance Liabilities	5,923,463	6,058,046
Derivative Liabilities	43,936	54,320
Global Public Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	32,471,073	35,732,858
Insurance Assets	465,923	531,519
Insurance Liabilities	545,760	604,339
Derivative Liabilities	26,625	27,112
Collateralized Debt Obligations [Member] \| Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	1,317,071	2,092,072
Insurance Assets	1,416	3,867
Insurance Liabilities	4,677	7,119
Derivative Liabilities	4,925	10,092
Residential Mortgage-Backed Securities [Member] \| Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	16,958,514	19,231,335
Insurance Assets	549,303	581,498
Insurance Liabilities	4,029,415	3,890,937
Derivative Liabilities
Other Consumer Asset-Backed [Member] \| Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	5,191,120	5,425,583
Insurance Assets	66,556	68,511
Insurance Liabilities	907,591	992,177
Derivative Liabilities	0	0
Other Commercial Asset-Backed [Member] \| Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	5,069,719	7,237,953
Insurance Assets	376,164	429,559
Insurance Liabilities	402,744	559,600
Derivative Liabilities	36,275	39,916
Other [Member] \| Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	4,195,483	4,347,287
Insurance Assets	99,350	113,468
Insurance Liabilities	579,036	608,213
Derivative Liabilities	$ 2,736	$ 4,312

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

Sep. 30, 2014

Dec. 31, 2013

Variable Interest Entities [Line Items]

Maximum Exposure To Loss

$ 65,202,980

$ 74,067,088

Insurance Assets

1,558,712

1,728,422

Insurance Liabilities

6,469,223

6,662,385