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	6 Months Ended	12 Months Ended
	Jun. 30, 2016 USD ($) Policies	Dec. 31, 2015 USD ($) Policies
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	299	293
Remaining weighted-average contract period (in years)	16 years	15 years
Gross insured contractual payments outstanding:
Principal	$ 14,825,587	$ 15,976,009
Interest	11,578,834	11,867,941
Total	26,404,421	27,843,950
Gross undiscounted claim liability	7,492,096	8,192,193
Discount, gross claim liability	881,089	1,333,663
Gross claim liability before all subrogation and before reinsurance	6,611,007	6,858,530
Less:
Gross RMBS subrogation	(1,892,727)	(2,841,291)
Discount, RMBS subrogation	8,901	11,716
Discounted RMBS subrogation, before reinsurance	(1,883,826)	(2,829,575)
Less:
Gross other subrogation	(1,173,303)	(1,388,070)
Discount, other subrogation	184,637	334,251
Discounted other subrogation, before reinsurance	(988,666)	(1,053,819)
Gross claim liability, net of all subrogation and discounts, before reinsurance	3,738,515	2,975,136
Less: Unearned premium reserves	(161,136)	(189,587)
Plus: Loss adjustment expenses reserves	73,402	73,264
Claim liability reported on Balance Sheet, before reinsurance	3,650,781	2,858,813
Reinsurance recoverable reported on Balance Sheet	$ 28,704	$ 43,999
I/SL [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	41	33
Remaining weighted-average contract period (in years)	9 years	9 years
Gross insured contractual payments outstanding:
Principal	$ 1,902,757	$ 1,830,549
Interest	760,420	724,940
Total	2,663,177	2,555,489
Gross undiscounted claim liability	7,163	6,188
Discount, gross claim liability	394	515
Gross claim liability before all subrogation and before reinsurance	6,769	5,673
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	6,769	5,673
Less: Unearned premium reserves	(4,093)	(3,360)
Plus: Loss adjustment expenses reserves	4,238	0
Claim liability reported on Balance Sheet, before reinsurance	6,914	2,313
Reinsurance recoverable reported on Balance Sheet	$ 749	$ 642
IA [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	14	14
Remaining weighted-average contract period (in years)	16 years	17 years
Gross insured contractual payments outstanding:
Principal	$ 259,528	$ 263,288
Interest	111,177	107,624
Total	370,705	370,912
Gross undiscounted claim liability	5,486	5,632
Discount, gross claim liability	434	652
Gross claim liability before all subrogation and before reinsurance	5,052	4,980
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	5,052	4,980
Less: Unearned premium reserves	(1,792)	(1,796)
Plus: Loss adjustment expenses reserves	59	66
Claim liability reported on Balance Sheet, before reinsurance	3,319	3,250
Reinsurance recoverable reported on Balance Sheet	$ 943	$ 880
II [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	26	23
Remaining weighted-average contract period (in years)	28 years	26 years
Gross insured contractual payments outstanding:
Principal	$ 1,910,439	$ 1,912,237
Interest	6,820,692	6,834,538
Total	8,731,131	8,746,775
Gross undiscounted claim liability	187,914	173,930
Discount, gross claim liability	88,856	96,218
Gross claim liability before all subrogation and before reinsurance	99,058	77,712
Less:
Gross RMBS subrogation	(1,666)	0
Discount, RMBS subrogation	7	0
Discounted RMBS subrogation, before reinsurance	(1,659)	0
Less:
Gross other subrogation	(8,747)	(12,937)
Discount, other subrogation	2,078	3,961
Discounted other subrogation, before reinsurance	(6,669)	(8,976)
Gross claim liability, net of all subrogation and discounts, before reinsurance	90,730	68,736
Less: Unearned premium reserves	(47,390)	(48,871)
Plus: Loss adjustment expenses reserves	383	629
Claim liability reported on Balance Sheet, before reinsurance	43,723	20,494
Reinsurance recoverable reported on Balance Sheet	$ 187	$ 85
III [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	48	63
Remaining weighted-average contract period (in years)	18 years	19 years
Gross insured contractual payments outstanding:
Principal	$ 2,107,764	$ 2,972,615
Interest	1,469,457	1,792,525
Total	3,577,221	4,765,140
Gross undiscounted claim liability	980,082	1,595,525
Discount, gross claim liability	225,668	458,805
Gross claim liability before all subrogation and before reinsurance	754,414	1,136,720
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	(259,739)	(526,957)
Discount, other subrogation	71,083	198,643
Discounted other subrogation, before reinsurance	(188,656)	(328,314)
Gross claim liability, net of all subrogation and discounts, before reinsurance	565,758	808,406
Less: Unearned premium reserves	(40,302)	(63,257)
Plus: Loss adjustment expenses reserves	14,768	15,090
Claim liability reported on Balance Sheet, before reinsurance	540,224	760,239
Reinsurance recoverable reported on Balance Sheet	$ 43,089	$ 59,503
IV [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	167	157
Remaining weighted-average contract period (in years)	15 years	13 years
Gross insured contractual payments outstanding:
Principal	$ 8,595,851	$ 8,942,730
Interest	2,401,664	2,391,523
Total	10,997,515	11,334,253
Gross undiscounted claim liability	6,246,780	6,339,537
Discount, gross claim liability	561,883	770,694
Gross claim liability before all subrogation and before reinsurance	5,684,897	5,568,843
Less:
Gross RMBS subrogation	(1,891,061)	(2,841,291)
Discount, RMBS subrogation	8,894	11,716
Discounted RMBS subrogation, before reinsurance	(1,882,167)	(2,829,575)
Less:
Gross other subrogation	(891,879)	(835,078)
Discount, other subrogation	108,569	127,669
Discounted other subrogation, before reinsurance	(783,310)	(707,409)
Gross claim liability, net of all subrogation and discounts, before reinsurance	3,019,420	2,031,859
Less: Unearned premium reserves	(67,141)	(71,848)
Plus: Loss adjustment expenses reserves	53,954	57,479
Claim liability reported on Balance Sheet, before reinsurance	3,006,233	2,017,490
Reinsurance recoverable reported on Balance Sheet	$ (16,264)	$ (17,111)
V [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	3	3
Remaining weighted-average contract period (in years)	6 years	6 years
Gross insured contractual payments outstanding:
Principal	$ 49,248	$ 54,590
Interest	15,424	16,791
Total	64,672	71,381
Gross undiscounted claim liability	64,671	71,381
Discount, gross claim liability	3,854	6,779
Gross claim liability before all subrogation and before reinsurance	60,817	64,602
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	(12,938)	(13,098)
Discount, other subrogation	2,907	3,978
Discounted other subrogation, before reinsurance	(10,031)	(9,120)
Gross claim liability, net of all subrogation and discounts, before reinsurance	50,786	55,482
Less: Unearned premium reserves	(418)	(455)
Plus: Loss adjustment expenses reserves	0	0
Claim liability reported on Balance Sheet, before reinsurance	50,368	55,027
Reinsurance recoverable reported on Balance Sheet	$ 0	$ 0