Financial Guarantee Insurance Contracts - Summary of Information Related to Policies Currently Included in Ambac's Loss Reserves or Subrogation Recoverable (Detail) - Successor [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) Policies	Dec. 31, 2014 USD ($) Policies	Dec. 31, 2013 USD ($)	Apr. 30, 2013 USD ($)
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	293	325
Remaining weighted-average contract period (in years)	15 years	16 years
Gross insured contractual payments outstanding:
Principal	$ 15,976,009	$ 18,322,914
Interest	11,867,941	7,254,995
Total	27,843,950	25,577,909
Gross undiscounted claim liability	8,192,193	8,679,974
Discount, gross claim liability	1,333,663	1,509,948
Gross claim liability before all subrogation and before reinsurance	6,858,530	7,170,026
Less:
Gross RMBS subrogation	(2,841,291)	(2,541,219)
Discount, RMBS subrogation	11,716	17,679
Discounted RMBS subrogation, before reinsurance	(2,829,575)	(2,523,540)	$ (2,206,598)	$ (2,482,918)
Less:
Gross other subrogation	(1,388,070)	(792,287)
Discount, other subrogation	334,251	91,808
Discounted other subrogation, before reinsurance	(1,053,819)	(700,479)
Gross claim liability, net of all subrogation and discounts, before reinsurance	2,975,136	3,946,007
Less: Unearned premium reserves	(189,587)	(241,348)
Plus: Loss adjustment expenses reserves	73,264	94,074
Claim liability reported on Balance Sheet, before reinsurance	2,858,813	3,798,733
Reinsurance recoverable reported on Balance Sheet	$ 43,999	$ 99,838
I/SL [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	33	36
Remaining weighted-average contract period (in years)	9 years	8 years
Gross insured contractual payments outstanding:
Principal	$ 1,830,549	$ 1,026,513
Interest	724,940	418,746
Total	2,555,489	1,445,259
Gross undiscounted claim liability	6,188	16,360
Discount, gross claim liability	515	1,147
Gross claim liability before all subrogation and before reinsurance	5,673	15,213
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	0	0
Discount, other subrogation	0	0
Discounted other subrogation, before reinsurance	0	0
Gross claim liability, net of all subrogation and discounts, before reinsurance	5,673	15,213
Less: Unearned premium reserves	(3,360)	(10,945)
Plus: Loss adjustment expenses reserves	0	3
Claim liability reported on Balance Sheet, before reinsurance	2,313	4,271
Reinsurance recoverable reported on Balance Sheet	$ 642	$ 73
IA [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	14	26
Remaining weighted-average contract period (in years)	17 years	12 years
Gross insured contractual payments outstanding:
Principal	$ 263,288	$ 519,291
Interest	107,624	212,296
Total	370,912	731,587
Gross undiscounted claim liability	5,632	11,525
Discount, gross claim liability	652	937
Gross claim liability before all subrogation and before reinsurance	4,980	10,588
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	0	0
Discount, other subrogation	0	0
Discounted other subrogation, before reinsurance	0	0
Gross claim liability, net of all subrogation and discounts, before reinsurance	4,980	10,588
Less: Unearned premium reserves	(1,796)	(3,432)
Plus: Loss adjustment expenses reserves	66	1,303
Claim liability reported on Balance Sheet, before reinsurance	3,250	8,459
Reinsurance recoverable reported on Balance Sheet	$ 880	$ 890
II [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	23	33
Remaining weighted-average contract period (in years)	26 years	15 years
Gross insured contractual payments outstanding:
Principal	$ 1,912,237	$ 3,091,744
Interest	6,834,538	1,878,770
Total	8,746,775	4,970,514
Gross undiscounted claim liability	173,930	155,488
Discount, gross claim liability	96,218	16,438
Gross claim liability before all subrogation and before reinsurance	77,712	139,050
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	(12,937)	(18,034)
Discount, other subrogation	3,961	6,069
Discounted other subrogation, before reinsurance	(8,976)	(11,965)
Gross claim liability, net of all subrogation and discounts, before reinsurance	68,736	127,085
Less: Unearned premium reserves	(48,871)	(73,749)
Plus: Loss adjustment expenses reserves	629	1,968
Claim liability reported on Balance Sheet, before reinsurance	20,494	55,304
Reinsurance recoverable reported on Balance Sheet	$ 85	$ 1,355
III [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	63	69
Remaining weighted-average contract period (in years)	19 years	21 years
Gross insured contractual payments outstanding:
Principal	$ 2,972,615	$ 3,792,559
Interest	1,792,525	2,765,537
Total	4,765,140	6,558,096
Gross undiscounted claim liability	1,595,525	2,040,402
Discount, gross claim liability	458,805	716,812
Gross claim liability before all subrogation and before reinsurance	1,136,720	1,323,590
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	(526,957)	(127,143)
Discount, other subrogation	198,643	36,779
Discounted other subrogation, before reinsurance	(328,314)	(90,364)
Gross claim liability, net of all subrogation and discounts, before reinsurance	808,406	1,233,226
Less: Unearned premium reserves	(63,257)	(88,332)
Plus: Loss adjustment expenses reserves	15,090	6,470
Claim liability reported on Balance Sheet, before reinsurance	760,239	1,151,364
Reinsurance recoverable reported on Balance Sheet	$ 59,503	$ 110,957
IV [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	157	160
Remaining weighted-average contract period (in years)	13 years	12 years
Gross insured contractual payments outstanding:
Principal	$ 8,942,730	$ 9,892,760
Interest	2,391,523	1,979,627
Total	11,334,253	11,872,387
Gross undiscounted claim liability	6,339,537	6,456,139
Discount, gross claim liability	770,694	774,611
Gross claim liability before all subrogation and before reinsurance	5,568,843	5,681,528
Less:
Gross RMBS subrogation	(2,841,291)	(2,541,219)
Discount, RMBS subrogation	11,716	17,679
Discounted RMBS subrogation, before reinsurance	(2,829,575)	(2,523,540)
Less:
Gross other subrogation	(835,078)	(647,110)
Discount, other subrogation	127,669	48,960
Discounted other subrogation, before reinsurance	(707,409)	(598,150)
Gross claim liability, net of all subrogation and discounts, before reinsurance	2,031,859	2,559,838
Less: Unearned premium reserves	(71,848)	(64,890)
Plus: Loss adjustment expenses reserves	57,479	84,330
Claim liability reported on Balance Sheet, before reinsurance	2,017,490	2,579,278
Reinsurance recoverable reported on Balance Sheet	$ (17,111)	$ (13,437)
V [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	3	1
Remaining weighted-average contract period (in years)	6 years	6 years
Gross insured contractual payments outstanding:
Principal	$ 54,590	$ 47
Interest	16,791	19
Total	71,381	66
Gross undiscounted claim liability	71,381	60
Discount, gross claim liability	6,779	3
Gross claim liability before all subrogation and before reinsurance	64,602	57
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	(13,098)	0
Discount, other subrogation	3,978	0
Discounted other subrogation, before reinsurance	(9,120)	0
Gross claim liability, net of all subrogation and discounts, before reinsurance	55,482	57
Less: Unearned premium reserves	(455)	0
Plus: Loss adjustment expenses reserves	0	0
Claim liability reported on Balance Sheet, before reinsurance	55,027	57
Reinsurance recoverable reported on Balance Sheet	$ 0	$ 0