Special Purpose Entities, Including Variable Interest Entities (Details 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Summary of carrying amount of the assets, liabilities and maximum exposure to loss of Ambac's variable interests in non-consolidated VIEs
Maximum Exposure To Loss	$ 101,338,741	$ 111,748,270
Insurance Assets	1,895,880	2,196,161
Insurance Liabilities	9,421,753	9,207,107
Derivative Liabilities	201,946	183,666
Collateralized debt obligations [Member]
Summary of carrying amount of the assets, liabilities and maximum exposure to loss of Ambac's variable interests in non-consolidated VIEs
Maximum Exposure To Loss	12,408,367	14,093,243
Insurance Assets	12,834	15,096
Insurance Liabilities	20,677	105,219
Derivative Liabilities	119,319	120,614
Mortgage-backed-residential [Member]
Summary of carrying amount of the assets, liabilities and maximum exposure to loss of Ambac's variable interests in non-consolidated VIEs
Maximum Exposure To Loss	27,072,283	30,307,753
Insurance Assets	597,836	783,329
Insurance Liabilities	5,483,692	5,396,711
Mortgage-backed-commercial [Member]
Summary of carrying amount of the assets, liabilities and maximum exposure to loss of Ambac's variable interests in non-consolidated VIEs
Maximum Exposure To Loss	646,669	685,870
Derivative Liabilities	6,196	6,241
Other consumer asset-backed [Member]
Summary of carrying amount of the assets, liabilities and maximum exposure to loss of Ambac's variable interests in non-consolidated VIEs
Maximum Exposure To Loss	7,072,240	7,851,980
Insurance Assets	125,354	129,234
Insurance Liabilities	1,184,897	1,315,146
Derivative Liabilities	42,853	35,583
Other asset-backed securities [Member]
Summary of carrying amount of the assets, liabilities and maximum exposure to loss of Ambac's variable interests in non-consolidated VIEs
Maximum Exposure To Loss	11,228,636	13,363,434
Insurance Assets	471,108	559,884
Insurance Liabilities	1,397,059	1,045,477
Derivative Liabilities	7,606	4,541
Other [Member]
Summary of carrying amount of the assets, liabilities and maximum exposure to loss of Ambac's variable interests in non-consolidated VIEs
Maximum Exposure To Loss	5,812,959	7,552,264
Insurance Assets	133,287	139,586
Insurance Liabilities	647,864	643,864
Derivative Liabilities	2,456	1,837
Global Structured Finance [Member]
Summary of carrying amount of the assets, liabilities and maximum exposure to loss of Ambac's variable interests in non-consolidated VIEs
Maximum Exposure To Loss	64,241,154	73,854,544
Insurance Assets	1,340,419	1,627,129
Insurance Liabilities	8,734,189	8,506,417
Derivative Liabilities	178,430	168,816
Global Public Finance [Member]
Summary of carrying amount of the assets, liabilities and maximum exposure to loss of Ambac's variable interests in non-consolidated VIEs
Maximum Exposure To Loss	37,097,587	37,893,726
Insurance Assets	555,461	569,032
Insurance Liabilities	687,564	700,690
Derivative Liabilities	$ 23,516	$ 14,850