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] - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	$ 51,183,727
Insurance Assets	1,267,861
Insurance Liabilities	4,312,457
Successor [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss		$ 56,182,335
Insurance Assets		1,889,722
Insurance Liabilities		4,202,322
Derivative Liabilities	(159,998)	(138,975)
Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	24,316,176
Insurance Assets	901,880
Insurance Liabilities	3,914,190
Global Structured Finance [Member] | Successor [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss		27,595,753
Insurance Assets		1,512,310
Insurance Liabilities		3,775,023
Derivative Liabilities	(150,391)	(114,115)
Global Public Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	26,867,551
Insurance Assets	365,981
Insurance Liabilities	398,267
Global Public Finance [Member] | Successor [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss		28,586,582
Insurance Assets		377,412
Insurance Liabilities		427,299
Derivative Liabilities	(9,607)	(24,860)
Collateralized Debt Obligations [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	903,540
Insurance Assets	232
Insurance Liabilities	3,469
Collateralized Debt Obligations [Member] | Global Structured Finance [Member] | Successor [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss		980,935
Insurance Assets		264
Insurance Liabilities		3,639
Derivative Liabilities	(167,626)	(129,525)
Residential Mortgage-Backed Securities [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	15,988,051
Insurance Assets	723,524
Insurance Liabilities	3,022,345
Residential Mortgage-Backed Securities [Member] | Global Structured Finance [Member] | Successor [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss		17,081,002
Insurance Assets		1,279,650
Insurance Liabilities		2,680,739
Other Consumer Asset-Backed [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	2,454,061
Insurance Assets	28,599
Insurance Liabilities	329,172
Other Consumer Asset-Backed [Member] | Global Structured Finance [Member] | Successor [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss		3,853,443
Insurance Assets		47,346
Insurance Liabilities		535,090
Derivative Liabilities	0	0
Other Commercial Asset-Backed [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	1,885,561
Insurance Assets	76,941
Insurance Liabilities	72,606
Other Commercial Asset-Backed [Member] | Global Structured Finance [Member] | Successor [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss		2,393,805
Insurance Assets		104,033
Insurance Liabilities		94,191
Derivative Liabilities	0	0
Other [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	3,084,963
Insurance Assets	72,584
Insurance Liabilities	486,598
Other [Member] | Global Structured Finance [Member] | Successor [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss		3,286,568
Insurance Assets		81,017
Insurance Liabilities		461,364
Derivative Liabilities	$ 17,235	$ 15,410