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	3 Months Ended	12 Months Ended
	Mar. 31, 2016 USD ($) Policies	Dec. 31, 2015 USD ($) Policies
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	308	293
Remaining weighted-average contract period (in years)	16 years	15 years
Gross insured contractual payments outstanding:
Principal	$ 15,599,434	$ 15,976,009
Interest	11,883,312	11,867,941
Total	27,482,746	27,843,950
Gross undiscounted claim liability	7,764,322	8,192,193
Discount, gross claim liability	1,026,497	1,333,663
Gross claim liability before all subrogation and before reinsurance	6,737,825	6,858,530
Less:
Gross RMBS subrogation	(1,861,904)	(2,841,291)
Discount, RMBS subrogation	6,831	11,716
Discounted RMBS subrogation, before reinsurance	(1,855,073)	(2,829,575)
Less:
Gross other subrogation	(1,409,009)	(1,388,070)
Discount, other subrogation	268,016	334,251
Discounted other subrogation, before reinsurance	(1,140,993)	(1,053,819)
Gross claim liability, net of all subrogation and discounts, before reinsurance	3,741,759	2,975,136
Less: Unearned premium reserves	(167,941)	(189,587)
Plus: Loss adjustment expenses reserves	69,258	73,264
Claim liability reported on Balance Sheet, before reinsurance	3,643,076	2,858,813
Reinsurance recoverable reported on Balance Sheet	$ 27,316	$ 43,999
I/SL [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	40	33
Remaining weighted-average contract period (in years)	10 years	9 years
Gross insured contractual payments outstanding:
Principal	$ 2,217,143	$ 1,830,549
Interest	962,608	724,940
Total	3,179,751	2,555,489
Gross undiscounted claim liability	7,717	6,188
Discount, gross claim liability	534	515
Gross claim liability before all subrogation and before reinsurance	7,183	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	7,183	5,673
Less: Unearned premium reserves	(4,411)	(3,360)
Plus: Loss adjustment expenses reserves	1,907	0
Claim liability reported on Balance Sheet, before reinsurance	4,679	2,313
Reinsurance recoverable reported on Balance Sheet	$ 722	$ 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)	17 years	17 years
Gross insured contractual payments outstanding:
Principal	$ 262,318	$ 263,288
Interest	107,335	107,624
Total	369,653	370,912
Gross undiscounted claim liability	5,630	5,632
Discount, gross claim liability	502	652
Gross claim liability before all subrogation and before reinsurance	5,128	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	5,128	4,980
Less: Unearned premium reserves	(1,767)	(1,796)
Plus: Loss adjustment expenses reserves	64	66
Claim liability reported on Balance Sheet, before reinsurance	3,425	3,250
Reinsurance recoverable reported on Balance Sheet	$ 920	$ 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)	26 years	26 years
Gross insured contractual payments outstanding:
Principal	$ 1,962,283	$ 1,912,237
Interest	6,835,208	6,834,538
Total	8,797,491	8,746,775
Gross undiscounted claim liability	165,930	173,930
Discount, gross claim liability	83,763	96,218
Gross claim liability before all subrogation and before reinsurance	82,167	77,712
Less:
Gross RMBS subrogation	(1,203)	0
Discount, RMBS subrogation	4	0
Discounted RMBS subrogation, before reinsurance	(1,199)	0
Less:
Gross other subrogation	(10,907)	(12,937)
Discount, other subrogation	2,731	3,961
Discounted other subrogation, before reinsurance	(8,176)	(8,976)
Gross claim liability, net of all subrogation and discounts, before reinsurance	72,792	68,736
Less: Unearned premium reserves	(48,102)	(48,871)
Plus: Loss adjustment expenses reserves	275	629
Claim liability reported on Balance Sheet, before reinsurance	24,965	20,494
Reinsurance recoverable reported on Balance Sheet	$ 104	$ 85
III [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	59	63
Remaining weighted-average contract period (in years)	17 years	19 years
Gross insured contractual payments outstanding:
Principal	$ 2,440,917	$ 2,972,615
Interest	1,619,094	1,792,525
Total	4,060,011	4,765,140
Gross undiscounted claim liability	1,259,532	1,595,525
Discount, gross claim liability	291,056	458,805
Gross claim liability before all subrogation and before reinsurance	968,476	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	(502,340)	(526,957)
Discount, other subrogation	159,858	198,643
Discounted other subrogation, before reinsurance	(342,482)	(328,314)
Gross claim liability, net of all subrogation and discounts, before reinsurance	625,994	808,406
Less: Unearned premium reserves	(43,791)	(63,257)
Plus: Loss adjustment expenses reserves	13,486	15,090
Claim liability reported on Balance Sheet, before reinsurance	595,689	760,239
Reinsurance recoverable reported on Balance Sheet	$ 40,904	$ 59,503
IV [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	166	157
Remaining weighted-average contract period (in years)	15 years	13 years
Gross insured contractual payments outstanding:
Principal	$ 8,662,183	$ 8,942,730
Interest	2,342,277	2,391,523
Total	11,004,460	11,334,253
Gross undiscounted claim liability	6,254,134	6,339,537
Discount, gross claim liability	645,766	770,694
Gross claim liability before all subrogation and before reinsurance	5,608,368	5,568,843
Less:
Gross RMBS subrogation	(1,860,701)	(2,841,291)
Discount, RMBS subrogation	6,827	11,716
Discounted RMBS subrogation, before reinsurance	(1,853,874)	(2,829,575)
Less:
Gross other subrogation	(882,664)	(835,078)
Discount, other subrogation	102,074	127,669
Discounted other subrogation, before reinsurance	(780,590)	(707,409)
Gross claim liability, net of all subrogation and discounts, before reinsurance	2,973,904	2,031,859
Less: Unearned premium reserves	(69,434)	(71,848)
Plus: Loss adjustment expenses reserves	53,526	57,479
Claim liability reported on Balance Sheet, before reinsurance	2,957,996	2,017,490
Reinsurance recoverable reported on Balance Sheet	$ (15,334)	$ (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	$ 54,590	$ 54,590
Interest	16,790	16,791
Total	71,380	71,381
Gross undiscounted claim liability	71,379	71,381
Discount, gross claim liability	4,876	6,779
Gross claim liability before all subrogation and before reinsurance	66,503	64,602
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	(13,098)	(13,098)
Discount, other subrogation	3,353	3,978
Discounted other subrogation, before reinsurance	(9,745)	(9,120)
Gross claim liability, net of all subrogation and discounts, before reinsurance	56,758	55,482
Less: Unearned premium reserves	(436)	(455)
Plus: Loss adjustment expenses reserves	0	0
Claim liability reported on Balance Sheet, before reinsurance	56,322	55,027
Reinsurance recoverable reported on Balance Sheet	$ 0	$ 0