Consolidated Statements of Total Comprehensive Income - USD ($) $ in Thousands	4 Months Ended	8 Months Ended	12 Months Ended
	Apr. 30, 2013	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Successor [Member]
Revenues:
Net premiums earned		$ 213,518	$ 312,595	$ 246,360
Net investment income:
Securities available-for-sale and short-term		142,866	249,337	292,838
Other investments		3,580	16,952	8,108
Total net investment income		146,446	266,289	300,946
Other-than-temporary impairment losses:
Total other-than-temporary impairment losses		(47,418)	(66,692)	(26,632)
Portion of other -than-temporary impairment recognized in other comprehensive income		654	41,033	838
Net other-than-temporary impairments		(46,764)	(25,659)	(25,794)
Net realized investment gains		4,467	53,476	58,777
Change in fair value of credit derivatives:
Realized gains and other settlements		9,778	2,785	3,043
Unrealized gains (losses)		183,091	38,916	20,863
Net change in fair value of credit derivatives		192,869	41,701	23,906
Derivative products		114,771	(42,544)	(181,087)
Net realized gains (losses) on extinguishment of debt		0	81	(74,724)
Other income		4,364	7,150	12,498
Income (loss) on variable interest entities		(48,623)	31,569	(32,212)
Total revenues before expenses and reorganization items		581,048	644,658	328,670
Expenses:
Losses and loss expenses (benefit)		(185,138)	(768,707)	(545,574)
Insurance intangible amortization		99,658	169,557	151,830
Underwriting and operating expenses		68,769	102,702	101,474
Interest expense		84,950	116,537	127,476
Goodwill, Impairment Loss			514,511	0
Total expenses (benefit) before reorganization items		68,239	134,600	(164,794)
Pre-tax income before reorganization items		512,809	510,058	493,464
Reorganization items		493	0	211
Pre-tax income		512,316	510,058	493,253
Provision for income taxes		7,514	17,364	9,557
Net income (loss)		504,802	492,694	483,696
Less: net (gain) loss attributable to noncontrolling interest		(417)	(709)	(375)
Net income attributable to common shareholders		505,219	493,403	484,071
Other comprehensive income (loss), after tax:
Net income (loss)		504,802	492,694	483,696
Unrealized gains (losses) on securities, net of deferred income taxes of $0		(41,910)	(159,730)	252,603
Gains (losses) on foreign currency translation, net of deferred income taxes of $0		43,165	(45,025)	(43,599)
Changes to postretirement benefit, net of tax of $0		10,847	(687)	(816)
Total other comprehensive income (loss), net of tax		12,102	(205,442)	208,188
Total comprehensive income		516,904	287,252	691,884
Less: comprehensive (loss) gain attributable to the noncontrolling interest:
Net (gain) loss		(417)	(709)	(375)
Currency translation adjustments		441	(374)	(434)
Total comprehensive income attributable to Ambac Financial Group, Inc.		$ 516,880	$ 288,335	$ 692,693
Basic		$ 11.23	$ 10.92	$ 10.73
Diluted		$ 10.91	$ 10.72	$ 10.31
Predecessor [Member]
Revenues:
Net premiums earned	$ 130,000
Net investment income:
Securities available-for-sale and short-term	116,371
Other investments	369
Total net investment income	116,740
Other-than-temporary impairment losses:
Total other-than-temporary impairment losses	(467)
Portion of other -than-temporary impairment recognized in other comprehensive income	0
Net other-than-temporary impairments	(467)
Net realized investment gains	53,305
Change in fair value of credit derivatives:
Realized gains and other settlements	3,444
Unrealized gains (losses)	(63,828)
Net change in fair value of credit derivatives	(60,384)
Derivative products	(33,735)
Net realized gains (losses) on extinguishment of debt	0
Other income	8,363
Income (loss) on variable interest entities	426,566
Total revenues before expenses and reorganization items	640,388
Expenses:
Losses and loss expenses (benefit)	(38,056)
Insurance intangible amortization	0
Underwriting and operating expenses	44,566
Interest expense	31,025
Total expenses (benefit) before reorganization items	37,535
Pre-tax income before reorganization items	602,853
Reorganization items	(2,745,180)
Pre-tax income	3,348,033
Provision for income taxes	755
Net income (loss)	3,347,278
Less: net (gain) loss attributable to noncontrolling interest	(1,771)
Net income attributable to common shareholders	3,349,049
Other comprehensive income (loss), after tax:
Net income (loss)	3,347,278
Unrealized gains (losses) on securities, net of deferred income taxes of $0	175,347
Gains (losses) on foreign currency translation, net of deferred income taxes of $0	(428)
Changes to postretirement benefit, net of tax of $0	185
Total other comprehensive income (loss), net of tax	175,104
Total comprehensive income	3,522,382
Less: comprehensive (loss) gain attributable to the noncontrolling interest:
Net (gain) loss	(1,771)
Currency translation adjustments	229
Total comprehensive income attributable to Ambac Financial Group, Inc.	$ 3,523,924
Basic	$ 11.07
Diluted	$ 11.07