Consolidated Balance Sheets - Successor [Member] - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Assets:
Fixed income securities, at fair value (amortized cost: 2015—$4,813,186 and 2014—$4,514,878)	$ 4,892,421	$ 4,725,686
Fixed income securities pledged as collateral, at fair value (amortized cost: 2015—$34,732 and 2014—$64,378)	34,903	64,267
Short-term investments, at fair value (amortized cost: 2015—$197,070 and 2014—$360,069)	197,070	360,065
Other investments (includes 2015—$331,697 and 2014—$336,013 at fair value)	354,784	357,016
Total investments	5,479,178	5,507,034
Cash and cash equivalents	33,965	73,903
Receivable for securities	2,890	23,660
Investment income due and accrued	25,279	25,015
Premium receivables	936,924	1,000,607
Reinsurance recoverable on paid and unpaid losses	76,005	99,838
Deferred ceded premium	112,247	123,276
Subrogation recoverable	981,402	953,274
Loans	5,674	5,714
Derivative assets	80,661	109,017
Insurance intangible asset	1,339,427	1,410,920
Goodwill	514,511	514,511
Other assets	163,075	186,985
Total assets	25,513,636	25,159,864
Liabilities:
Unearned premiums	1,528,269	1,673,785
Loss and loss expense reserves	4,367,414	4,752,007
Ceded premiums payable	58,002	60,436
Obligations under investment agreements	112,215	160,079
Deferred taxes	1,955	2,079
Current taxes	1,670	5,701
Long-term debt	977,751	971,116
Accrued interest payable	339,006	304,139
Derivative liabilities	342,784	406,944
Other liabilities	57,653	63,396
Payable for securities purchased	5,494	762
Total liabilities	23,466,425	23,486,129
Stockholders’ equity:
Preferred stock, par value $0.01 per share; 20,000,000 shares authorized; issued and outstanding shares—none	0	0
Common stock, par value $0.01 per share; 130,000,000 shares authorized; issued and outstanding shares: 2015—45,006,139; 2014—45,005,932	450	450
Additional paid-in capital	190,414	189,138
Accumulated other comprehensive income	95,362	220,283
Accumulated earnings	1,486,696	989,290
Treasury stock, shares at cost: 2015—2,459; 2014—2,459	(56)	(56)
Total Ambac Financial Group, Inc. stockholders’ equity	1,772,866	1,399,105
Noncontrolling interest	274,345	274,630
Total stockholders’ equity	2,047,211	1,673,735
Total liabilities and stockholders’ equity	25,513,636	25,159,864
Variable Interest Entity, Primary Beneficiary [Member]
Assets:
Fixed income securities, at fair value (amortized cost: 2015—$4,813,186 and 2014—$4,514,878)	2,747,181	2,743,050
Investment income due and accrued	1,296	1,284
Other assets	2,761	2,891
Variable interest entity assets:
Restricted cash	5,944	7,708
Loans, at fair value	13,005,216	12,371,177
Liabilities:
Long-term debt	13,595,792	12,882,076
Accrued interest payable	3,244	3,268
Derivative liabilities	2,075,009	2,200,163
Other liabilities	$ 167	$ 178