Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Assets:
Fixed income securities, at fair value (amortized cost of $5,941,188 in 2014 and $5,927,254 in 2013)	$ 6,156,228	$ 5,885,316
Fixed income securities pledged as collateral, at fair value (amortized cost of $64,323 in 2014 and $126,196 in 2013)	64,031	126,223
Short-term investments, at fair value (amortized cost of $550,898 in 2014 and $271,118 in 2013)	550,900	271,119
Other investments (includes $270,791 at fair value in 2014 and $240,969 at fair value in 2013)	290,870	241,069
Total investments	7,062,029	6,523,727
Cash and Cash Equivalents, at Carrying Value	43,332	77,370
Receivable for securities	33,836	14,450
Investment income due and accrued	32,818	37,663
Premium receivables	1,266,632	1,453,021
Reinsurance recoverable on paid and unpaid losses	105,511	121,249
Deferred ceded premium	127,596	145,529
Subrogation recoverable	489,237	498,478
Loans	6,057	6,179
Derivative assets	91,320	77,711
Insurance intangible asset	1,475,012	1,597,965
Goodwill	514,511	514,511
Other assets	173,219	35,927
Variable interest entity assets:
Fixed income securities, at fair value	6,156,228	5,885,316
Investment income due and accrued	32,818	37,663
Other assets	173,219	35,927
Total assets	26,590,785	27,092,477
Liabilities:
Unearned premiums	1,953,392	2,255,680
Loss and loss expense reserves	6,003,474	5,968,712
Ceded premiums payable	61,104	70,962
Obligations under investment agreements	160,515	359,070
Deferred taxes	2,176	2,199
Current taxes	785	738
Long-term Debt	1,219,310	963,178
Accrued interest payable	376,773	294,817
Derivative liabilities	348,427	253,898
Other liabilities	66,101	67,377
Payable for securities purchased	27,263	4,654
Variable interest entity liabilities:
Accrued interest payable	376,773	294,817
Long-term debt, at fair value	1,219,310	963,178
Derivative liabilities	348,427	253,898
Other liabilities	66,101	67,377
Total liabilities	25,340,095	26,114,055
Stockholders’ equity:
Preferred stock, par value $0.01 per share; authorized shares—20,000,000; issued and outstanding shares—none	0	0
Common stock, par value $0.01 per share; authorized shares—130,000,000; issued and outstanding shares—00,000,000 at September 30, 2014 and 45,003,461 at December 31, 2013	450	450
Additional paid-in capital	188,648	185,672
Accumulated other comprehensive income	250,865	11,661
Accumulated earnings	535,706	505,219
Common stock held in treasury at cost, 937 shares at September 30, 2014 and December 31, 2013	(19)	(19)
Total Ambac Financial Group, Inc. stockholders’ equity	975,650	702,983
Noncontrolling interest	275,040	275,439
Total stockholders’ equity	1,250,690	978,422
Total liabilities and stockholders’ equity	26,590,785	27,092,477
Variable Interest Entity [Member]
Assets:
Fixed income securities, at fair value (amortized cost of $5,941,188 in 2014 and $5,927,254 in 2013)	2,651,683	2,475,182
Investment income due and accrued	4,192	1,365
Other assets	2,979	19,617
Variable interest entity assets:
Fixed income securities, at fair value	2,651,683	2,475,182
Restricted cash	7,337	17,498
Investment income due and accrued	4,192	1,365
Loans, at fair value	12,503,484	13,398,895
Intangible assets	0	76,140
Other assets	2,979	19,617
Liabilities:
Long-term Debt	13,159,174	14,091,753
Accrued interest payable	6,141	722
Derivative liabilities	1,955,291	1,772,306
Other liabilities	169	7,989
Variable interest entity liabilities:
Accrued interest payable	6,141	722
Long-term debt, at fair value	13,159,174	14,091,753
Derivative liabilities	1,955,291	1,772,306
Other liabilities	169	7,989
Successor [Member]
Assets:
Cash and Cash Equivalents, at Carrying Value	43,332	77,370
Derivative assets	91,320	77,711
Variable interest entity assets:
Total assets	26,590,785
Liabilities:
Derivative liabilities	348,427	253,898
Variable interest entity liabilities:
Derivative liabilities	348,427	253,898
Stockholders’ equity:
Accumulated other comprehensive income	250,865	11,661
Total stockholders’ equity	$ 1,250,690	$ 978,422