Consolidated Statements of Total Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	2 Months Ended	1 Months Ended	3 Months Ended	4 Months Ended	6 Months Ended
	Jun. 30, 2013 Successor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member]	Jun. 30, 2012 Predecessor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member]	Jun. 30, 2012 Predecessor Ambac [Member]
Revenues:
Net premiums earned	$ 58,039	$ 29,744	$ 103,042	$ 130,000	$ 197,992
Net investment income:
Securities available-for-sale and short-term	29,581	31,499	93,836	117,111	205,953
Other investments	(3,015)	912		369
Total net investment income	26,566	32,411	93,836	117,480	205,953
Other-than-temporary impairment losses:
Total other-than-temporary impairment losses	(2,004)	(467)	(7,492)	(467)	(10,431)
Portion of loss recognized in other comprehensive income	2		5,164		5,032
Net other-than-temporary impairment losses recognized in earnings	(2,002)	(467)	(2,328)	(467)	(5,399)
Net realized investment gains	18,472	7,245	67,067	53,305	67,459
Change in fair value of credit derivatives:
Realized gains and other settlements	6,074	935	3,073	3,444	6,327
Unrealized gains (losses)	45,146	(74,106)	(10,488)	(63,828)	(20,964)
Net change in fair value of credit derivatives	51,220	(73,171)	(7,415)	(60,384)	(14,637)
Derivative products	83,713	(33,166)	(124,091)	(33,735)	(77,134)
Net realized losses on extinguishment of debt			(177,745)		(177,745)
Other income	2,179	(1,135)	36,137	8,363	100,930
Income on variable interest entities	4,598	388,240	5,536	426,566	20,756
Total revenues before expenses and reorganization items	242,785	349,701	(5,961)	641,128	318,175
Expenses:
Losses and loss expenses	(26,117)	13,079	741,411	(38,056)	739,091
Insurance intangible amortization	24,952
Underwriting and operating expenses	16,587	10,877	33,567	45,306	70,101
Interest expense	21,144	7,860	31,855	31,025	65,694
Total expenses before reorganization items	36,566	31,816	806,833	38,275	874,886
Pre-tax income (loss) from continuing operations before reorganization items	206,219	317,885	(812,794)	602,853	(556,711)
Reorganization items	424	(2,747,239)	767	(2,745,180)	3,228
Pre-tax income (loss) from continuing operations	205,795	3,065,124	(813,561)	3,348,033	(559,939)
Provision (benefit) for income taxes	513	98	(211)	755	89
Net income (loss)	205,282	3,065,026	(813,350)	3,347,278	(560,028)
Less: net loss attributable to the noncontrolling interest	(399)	(1,724)	(2,232)	(1,771)	(2,230)
Net income (loss) attributable to common shareholders	205,681	3,066,750	(811,118)	3,349,049	(557,798)
Other comprehensive income (loss), after tax:
Net income (loss)	205,282	3,065,026	(813,350)	3,347,278	(560,028)
Unrealized (loss) gain on securities, net of deferred income taxes of $0	(90,983)	81,249	(23,063)	175,347	(39,915)
Loss on foreign currency translation, net of deferred income taxes of $0	(12,662)	(167)	(5,324)	(428)	(2,111)
Amortization of postretirement benefit, net of tax of $0		(623)		185	(3,792)
Total other comprehensive (loss)income, net of tax	(103,645)	80,459	(28,387)	175,104	(45,818)
Total comprehensive income (loss)	101,637	3,145,485	(841,737)	3,522,382	(605,846)
Less: comprehensive income (loss) attributable to the noncontrolling interest:
Net loss	(399)	(1,724)	(2,232)	(1,771)	(2,230)
Currency translation adjustments	(138)	270	(183)	229	(152)
Total comprehensive income (loss) attributable to Ambac Financial Group, Inc.	$ 102,174	$ 3,146,939	$ (839,322)	$ 3,523,924	$ (603,464)
Net income (loss) per share attributable to Ambac Financial Group, Inc. common shareholders	$ 4.57	$ 10.14	$ (2.68)	$ 11.07	$ (1.84)
Net income (loss) per diluted share attributable to Ambac Financial Group, Inc. common shareholders	$ 4.42	$ 10.14	$ (2.68)	$ 11.07	$ (1.84)