Consolidated Statements of Total Comprehensive Income (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenues:
Net premiums earned	$ 103,042	$ 99,271	$ 197,992	$ 191,070
Net investment income	93,836	95,639	205,953	172,107
Other-than-temporary impairments:
Total other-than-temporary impairment losses	(7,492)	(17,793)	(11,803)	(19,506)
Portion of loss recognized in other comprehensive income	5,164	215	6,404	215
Net other-than-temporary impairment losses recognized in earnings	(2,328)	(17,578)	(5,399)	(19,291)
Net realized investment gains (losses)	67,067	(2,528)	67,459	(78)
Change in fair value of credit derivatives:
Realized gains and other settlements	3,073	4,224	6,327	9,547
Unrealized (losses) gains	(10,488)	20,063	(20,964)	5,837
Net change in fair value of credit derivatives	(7,415)	24,287	(14,637)	15,384
Derivative products	(124,091)	(65,595)	(77,134)	(44,591)
Net realized (losses) gains on extinguishment of debt	(177,745)	3,119	(177,745)	3,119
Other income	36,137	9,227	100,930	37,530
Income (loss) on variable interest entities	5,536	2,353	20,756	(3,772)
Total revenues before expenses and reorganization items	(5,961)	148,195	318,175	351,478
Expenses:
Losses and loss expenses	741,411	196,398	739,091	1,116,045
Underwriting and operating expenses	33,567	15,533	70,101	61,000
Interest expense	31,855	31,670	65,694	61,930
Total expenses before reorganization items	806,833	243,601	874,886	1,238,975
Pre-tax loss from continuing operations before reorganization items	(812,794)	(95,406)	(556,711)	(887,497)
Reorganization items	767	6,470	3,228	31,275
Pre-tax loss from continuing operations	(813,561)	(101,876)	(559,939)	(918,772)
(Benefit) provision for income taxes	(211)	542	89	2,892
Net loss	(813,350)	(102,418)	(560,028)	(921,664)
Less: net (loss) income attributable to the noncontrolling interest	(2,232)	14	(2,230)	47
Loss attributable to common shareholders	(811,118)	(102,432)	(557,798)	(921,711)
Other comprehensive loss after tax:
Net loss	(813,350)	(102,418)	(560,028)	(921,664)
Unrealized gains on securities, net of deferred income taxes of $0	36,466	117,081	15,562	192,506
Less: reclassification adjustment for net gain (loss) included in net loss	59,529	(21,094)	55,477	(20,079)
(Loss) gain on foreign currency translation, net of deferred income taxes of $0	(5,324)	(291)	(2,111)	4,093
Amortization of postretirement benefit, net of tax		14	(3,792)	725
Total other comprehensive (loss) income, net of tax	(28,387)	137,898	(45,818)	217,403
Total comprehensive (loss) income	(841,737)	35,480	(605,846)	(704,261)
Less: comprehensive (loss) income attributable to the noncontrolling interest:
Noncontrolling interest in subsidiaries' earnings	(2,232)	14	(2,230)	47
Currency translation adjustments	(183)	(167)	(152)	(123)
Total comprehensive (loss) income attributable to Ambac Financial Group, Inc.	$ (839,322)	$ 35,633	$ (603,464)	$ (704,185)
Net loss per share attributable to Ambac Financial Group, Inc. common shareholders	$ (2.68)	$ (0.34)	$ (1.84)	$ (3.05)
Net loss per diluted share attributable to Ambac Financial Group, Inc. common shareholders	$ (2.68)	$ (0.34)	$ (1.84)	$ (3.05)
Weighted-average number of common shares outstanding:
Basic	302,469,196	302,467,255	302,467,762	302,410,881
Diluted	302,469,196	302,467,255	302,467,762	302,410,881