Consolidated Statements of Total Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	5 Months Ended	3 Months Ended	4 Months Ended	9 Months Ended
	Sep. 30, 2013 Successor Ambac [Member]	Sep. 30, 2013 Successor Ambac [Member]	Sep. 30, 2012 Predecessor Ambac [Member]	Apr. 30, 2013 Predecessor Ambac [Member]	Sep. 30, 2012 Predecessor Ambac [Member]
Revenues:
Net Premiums Earned	$ 70,949	$ 128,988	$ 113,074	$ 130,000	$ 311,066
Net investment income:
Securities available-for-sale and short-term	51,776	80,987	84,078	116,371	290,031
Other investments	350	(2,665)		369
Total net investment income	52,126	78,322	84,078	116,740	290,031
Other-than-temporary impairment losses:
Total other-than-temporary impairment losses	(38,553)	(40,557)	(2,501)	(467)	(14,304)
Portion of loss recognized in other comprehensive income	516	518	2,147		8,551
Net other-than-temporary impairment losses recognized in earnings	(38,037)	(40,039)	(354)	(467)	(5,753)
Net realized investment (losses) gains	(10,310)	8,162	3,162	53,305	70,621
Change in fair value of credit derivatives:
Realized gains and other settlements	1,580	7,654	2,944	3,444	9,271
Unrealized gains (losses)	29,614	74,760	24,496	(63,828)	3,532
Net change in fair value of credit derivatives	31,194	82,414	27,440	(60,384)	12,803
Derivative products	12,372	96,085	(36,007)	(33,735)	(113,141)
Net realized losses on extinguishment of debt					(177,745)
Other income (loss)	(1,751)	428	(368)	8,363	100,562
Income on variable interest entities	55,109	59,707	6,137	426,566	26,893
Total revenues before expenses and reorganization items	171,652	414,067	197,162	640,388	515,337
Expenses:
Losses and loss expenses	(154,290)	(180,407)	(18,745)	(38,056)	720,346
Insurance intangible amortization	37,473	62,425
Underwriting and operating expenses	25,047	41,264	33,347	44,566	103,448
Interest expense	31,817	52,961	23,268	31,025	88,962
Total (benefit) expenses before reorganization items	(59,953)	(23,757)	37,870	37,535	912,756
Pre-tax income (loss) from continuing operations before reorganization items	231,605	437,824	159,292	602,853	(397,419)
Reorganization items	4	428	1,252	(2,745,180)	4,480
Pre-tax income (loss) from continuing operations	231,601	437,396	158,040	3,348,033	(401,899)
Provision for income taxes	594	1,107	667	755	756
Net income (loss)	231,007	436,289	157,373	3,347,278	(402,655)
Less: net income (loss) attributable to the noncontrolling interest	32	(367)	(171)	(1,771)	(2,401)
Net income (loss) attributable to common shareholders	230,975	436,656	157,544	3,349,049	(400,254)
Other comprehensive income (loss), after tax:
Net income	231,007	436,289	157,373	3,347,278	(402,655)
Unrealized (loss) gain on securities, net of deferred income taxes of $0	53,877	(37,106)	108,807	175,347	68,892
Gain (loss) on foreign currency translation, net of deferred income taxes of $0	39,798	27,136	1,686	(428)	(425)
Amortization of postretirement benefit, net of tax of $0				185	(3,792)
Total other comprehensive (loss) income, net of tax	93,675	(9,970)	110,493	175,104	64,675
Total comprehensive income (loss)	324,682	426,319	267,866	3,522,382	(337,980)
Less: comprehensive income (loss) attributable to the noncontrolling interest:
Net income (loss)	32	(367)	(171)	(1,771)	(2,401)
Currency translation adjustments	414	276	117	229	(35)
Total comprehensive income (loss) attributable to Ambac Financial Group, Inc.	$ 324,236	$ 426,410	$ 267,920	$ 3,523,924	$ (335,544)
Net income (loss) per share attributable to Ambac Financial Group, Inc. common shareholders	$ 5.13	$ 9.70	$ 0.52	$ 11.07	$ (1.32)
Net income (loss) per diluted share attributable to Ambac Financial Group, Inc. common shareholders	$ 4.98	$ 9.40	$ 0.52	$ 11.07	$ (1.32)