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, 2015 USD ($) Policies	Dec. 31, 2014 USD ($) Policies	Jun. 30, 2014 USD ($)	Dec. 31, 2013 USD ($)
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	324	325
Remaining weighted-average contract period (in years)	15 years	16 years
Gross insured contractual payments outstanding:
Principal	$ 17,179,319	$ 18,322,914
Interest	6,261,299	7,254,995
Total	23,440,618	25,577,909
Gross undiscounted claim liability	8,108,253	8,679,974
Discount, gross claim liability	1,409,135	1,509,948
Gross claim liability before all subrogation and before reinsurance	6,699,118	7,170,026
Less:
Gross RMBS subrogation	(2,569,494)	(2,541,219)
Discount, RMBS subrogation	12,920	17,679
Discounted RMBS subrogation, before reinsurance	(2,556,574)	(2,523,540)	$ (2,284,424)	$ (2,206,598)
Less:
Gross other subrogation	(740,671)	(792,287)
Discount, other subrogation	82,778	91,808
Discounted other subrogation, before reinsurance	(657,893)	(700,479)
Gross claim liability, net of all subrogation and discounts, before reinsurance	3,484,651	3,946,007
Less: Unearned premium reserves	(185,329)	(241,348)
Plus: Loss adjustment expenses reserves	86,690	94,074
Claim liability reported on Balance Sheet, before reinsurance	3,386,012	3,798,733
Reinsurance recoverable reported on Balance Sheet	$ 76,005	$ 99,838
I/SL [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	39	36
Remaining weighted-average contract period (in years)	7 years	8 years
Gross insured contractual payments outstanding:
Principal	$ 2,080,087	$ 1,026,513
Interest	733,337	418,746
Total	2,813,424	1,445,259
Gross undiscounted claim liability	14,688	16,360
Discount, gross claim liability	833	1,147
Gross claim liability before all subrogation and before reinsurance	13,855	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	13,855	15,213
Less: Unearned premium reserves	(10,512)	(10,945)
Plus: Loss adjustment expenses reserves	0	3
Claim liability reported on Balance Sheet, before reinsurance	3,343	4,271
Reinsurance recoverable reported on Balance Sheet	$ 274	$ 73
IA [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	18	26
Remaining weighted-average contract period (in years)	16 years	12 years
Gross insured contractual payments outstanding:
Principal	$ 385,118	$ 519,291
Interest	158,442	212,296
Total	543,560	731,587
Gross undiscounted claim liability	6,265	11,525
Discount, gross claim liability	685	937
Gross claim liability before all subrogation and before reinsurance	5,580	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	5,580	10,588
Less: Unearned premium reserves	(2,121)	(3,432)
Plus: Loss adjustment expenses reserves	13	1,303
Claim liability reported on Balance Sheet, before reinsurance	3,472	8,459
Reinsurance recoverable reported on Balance Sheet	$ 899	$ 890
II [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	33	33
Remaining weighted-average contract period (in years)	14 years	15 years
Gross insured contractual payments outstanding:
Principal	$ 1,518,386	$ 3,091,744
Interest	425,025	1,878,770
Total	1,943,411	4,970,514
Gross undiscounted claim liability	47,307	155,488
Discount, gross claim liability	5,928	16,438
Gross claim liability before all subrogation and before reinsurance	41,379	139,050
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	(16,477)	(18,034)
Discount, other subrogation	4,448	6,069
Discounted other subrogation, before reinsurance	(12,029)	(11,965)
Gross claim liability, net of all subrogation and discounts, before reinsurance	29,350	127,085
Less: Unearned premium reserves	(18,984)	(73,749)
Plus: Loss adjustment expenses reserves	714	1,968
Claim liability reported on Balance Sheet, before reinsurance	11,080	55,304
Reinsurance recoverable reported on Balance Sheet	$ 62	$ 1,355
III [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	69	69
Remaining weighted-average contract period (in years)	19 years	21 years
Gross insured contractual payments outstanding:
Principal	$ 4,065,996	$ 3,792,559
Interest	3,028,085	2,765,537
Total	7,094,081	6,558,096
Gross undiscounted claim liability	1,837,013	2,040,402
Discount, gross claim liability	632,267	716,812
Gross claim liability before all subrogation and before reinsurance	1,204,746	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	(140,596)	(127,143)
Discount, other subrogation	42,937	36,779
Discounted other subrogation, before reinsurance	(97,659)	(90,364)
Gross claim liability, net of all subrogation and discounts, before reinsurance	1,107,087	1,233,226
Less: Unearned premium reserves	(88,332)	(88,332)
Plus: Loss adjustment expenses reserves	12,399	6,470
Claim liability reported on Balance Sheet, before reinsurance	1,031,154	1,151,364
Reinsurance recoverable reported on Balance Sheet	$ 90,351	$ 110,957
IV [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	162	160
Remaining weighted-average contract period (in years)	13 years	12 years
Gross insured contractual payments outstanding:
Principal	$ 9,075,142	$ 9,892,760
Interest	1,898,244	1,979,627
Total	10,973,386	11,872,387
Gross undiscounted claim liability	6,130,231	6,456,139
Discount, gross claim liability	762,058	774,611
Gross claim liability before all subrogation and before reinsurance	5,368,173	5,681,528
Less:
Gross RMBS subrogation	(2,569,494)	(2,541,219)
Discount, RMBS subrogation	12,920	17,679
Discounted RMBS subrogation, before reinsurance	(2,556,574)	(2,523,540)
Less:
Gross other subrogation	(570,379)	(647,110)
Discount, other subrogation	31,211	48,960
Discounted other subrogation, before reinsurance	(539,168)	(598,150)
Gross claim liability, net of all subrogation and discounts, before reinsurance	2,272,431	2,559,838
Less: Unearned premium reserves	(64,886)	(64,890)
Plus: Loss adjustment expenses reserves	73,528	84,330
Claim liability reported on Balance Sheet, before reinsurance	2,281,073	2,579,278
Reinsurance recoverable reported on Balance Sheet	$ (15,581)	$ (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	18,166	19
Total	72,756	66
Gross undiscounted claim liability	72,749	60
Discount, gross claim liability	7,364	3
Gross claim liability before all subrogation and before reinsurance	65,385	57
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	(13,219)	0
Discount, other subrogation	4,182	0
Discounted other subrogation, before reinsurance	(9,037)	0
Gross claim liability, net of all subrogation and discounts, before reinsurance	56,348	57
Less: Unearned premium reserves	(494)	0
Plus: Loss adjustment expenses reserves	36	0
Claim liability reported on Balance Sheet, before reinsurance	55,890	57
Reinsurance recoverable reported on Balance Sheet	$ 0	$ 0