Ambac Financial (AMBC) 10-Q 9 Nov 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Nov. 06, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2015
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Trading Symbol	AMBC
Entity Registrant Name	AMBAC FINANCIAL GROUP INC
Entity Central Index Key	874,501
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		45,020,521

Consolidated Balance Sheets

Consolidated Balance Sheets - Successor [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets:
Fixed income securities, at fair value (amortized cost: 2015—$4,869,500 and 2014—$4,514,878)	$ 4,956,876	$ 4,725,686
Fixed income securities pledged as collateral, at fair value (amortized cost: 2015—$64,556 and 2014—$64,378)	64,972	64,267
Short-term investments, at fair value (amortized cost: 2015—$364,784 and 2014—$360,069)	364,780	360,065
Other investments (includes 2015—$290,723 and 2014—$336,013 at fair value)	314,934	357,016
Total investments	5,701,562	5,507,034
Cash and cash equivalents	27,099	73,903
Receivable for securities	9,749	23,660
Investment income due and accrued	25,113	25,015
Premium receivables	895,446	1,000,607
Reinsurance recoverable on paid and unpaid losses	68,319	99,838
Deferred ceded premium	105,673	123,276
Subrogation recoverable	982,202	953,274
Loans	5,499	5,714
Derivative assets	91,088	109,017
Income Taxes Receivable, Current	985	0
Insurance intangible asset	1,279,448	1,410,920
Goodwill	0	514,511
Other assets	199,294	186,985
Total assets	24,266,919	25,159,864
Liabilities:
Unearned premiums	1,428,230	1,673,785
Loss and loss expense reserves	4,237,515	4,752,007
Ceded premiums payable	57,651	60,436
Obligations under investment agreements	100,358	160,079
Deferred taxes	1,957	2,079
Current taxes	0	5,701
Long-term debt	1,123,003	971,116
Accrued interest payable	334,999	304,139
Derivative liabilities	375,835	406,944
Other liabilities	59,809	63,396
Payable for securities purchased	87,697	762
Total liabilities	22,637,882	23,486,129
Stockholders’ equity:
Preferred stock, par value $0.01 per share; 20,000,000 shares authorized; issued and outstanding shares—none	0	0
Common stock, par value $0.01 per share; 130,000,000 shares authorized; issued and outstanding shares: 45,036,587 and 45,005,932	450	450
Additional paid-in capital	189,981	189,138
Accumulated other comprehensive income	72,887	220,283
Accumulated earnings	1,091,946	989,290
Treasury stock, shares at cost: 16,066 and 2,459	(256)	(56)
Total Ambac Financial Group, Inc. stockholders’ equity	1,355,008	1,399,105
Noncontrolling interest	274,029	274,630
Total stockholders’ equity	1,629,037	1,673,735
Total liabilities and stockholders’ equity	24,266,919	25,159,864
Variable Interest Entity [Member]
Assets:
Fixed income securities, at fair value (amortized cost: 2015—$4,869,500 and 2014—$4,514,878)	2,679,895	2,743,050
Restricted Cash and Cash Equivalents	5,895	7,708
Investment income due and accrued	3,940	1,284
Loans Receivable, Net	12,183,061	12,371,177
Other assets	2,651	2,891
Liabilities:
Long-term debt	12,791,012	12,882,076
Accrued interest payable	5,855	3,268
Derivative liabilities	2,033,795	2,200,163
Other liabilities	$ 166	$ 178

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fixed income securities, amortized cost	$ 4,869,500	$ 4,514,878
ERROR in label resolution.	64,556	64,378
Short-term investments, amortized cost	364,784	360,069
Other investments	$ 290,723	$ 240,969
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	130,000,000	130,000,000
Common stock, shares issued	45,036,587	45,005,932
Common stock, shares outstanding	45,036,587	45,005,932
Treasury stock, shares	16,066	2,459

Consolidated Statements of Tota

Consolidated Statements of Total Comprehensive Income - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues:
Net premiums earned	$ 71,535	$ 64,831	$ 198,132	$ 212,391
Net investment income:
Securities available-for-sale and short-term	65,619	82,881	191,229	228,570
Other investments	(1,424)	700	10,702	5,905
Total net investment income	64,195	83,581	201,931	234,475
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	31,743	4,715	43,495	19,737
Other-than-temporary impairment losses:
Portion of other-than-temporary impairment recognized in other comprehensive income	22,593	(296)	30,206	(4,420)
Net other-than-temporary impairments	(9,150)	(5,011)	(13,289)	(24,157)
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments	2,106	10,045	50,854	29,401
Gain (Loss) on Sale of Derivatives	1,693	596	2,519	2,088
Change in fair value of credit derivatives:
Unrealized gains (losses)	35,259	6,820	42,227	11,491
Net change in fair value of credit derivatives	36,952	7,416	44,746	13,579
Derivative products	(65,083)	(15,685)	(51,858)	(117,511)
Net realized gains (losses) on extinguishment of debt	1,420	0	81	0
Other income (expense)	7,150	1,046	5,206	8,206
Income (loss) on variable interest entities	(21,435)	9,116	38,130	(34,574)
Total revenues	87,690	155,339	473,933	321,810
Expenses:
Losses and loss expense (benefit)	(133,213)	(28,698)	(431,642)	6,608
Insurance intangible amortization	39,680	41,908	115,200	109,878
Underwriting and operating expenses	25,006	25,513	75,402	75,332
Interest expense	29,899	31,841	85,980	96,122
Goodwill, Impairment Loss	514,511	0	514,511	0
Total expenses (benefit)	475,883	70,564	359,451	287,940
Pre-tax income (loss) before reorganization items	(388,193)	84,775	114,482	33,870
Reorganization items	0	2	0	211
Pre-tax income (loss)	(388,193)	84,773	114,482	33,659
Provision for income taxes	2,838	2,344	8,464	3,414
Net income (loss)	(391,031)	82,429	106,018	30,245
Less: net (gain) loss attributable to noncontrolling interest	(44)	(21)	(401)	(242)
Net income (loss) attributable to common shareholders	(390,987)	82,450	106,419	30,487
Other comprehensive income (loss), after tax:
Net income (loss)	(391,031)	82,429	106,018	30,245
Unrealized gains (losses) on securities, net of deferred income taxes of $0	8,382	(17,225)	(122,905)	256,660
Gains (losses) on foreign currency translation, net of deferred income taxes of $0	(30,909)	(38,429)	(24,224)	(17,001)
Changes to postretirement benefit, net of tax of $0	(220)	(204)	(467)	(612)
Total other comprehensive income (loss), net of tax	(22,747)	(55,858)	(147,596)	239,047
Total comprehensive income (loss)	(413,778)	26,571	(41,578)	269,292
Less: comprehensive (loss) gain attributable to the noncontrolling interest:
Net (gain) loss	(44)	(21)	(401)	(242)
Currency translation adjustments	(272)	(395)	(200)	(157)
Total comprehensive income (loss) attributable to Ambac Financial Group, Inc.	$ (413,462)	$ 26,987	$ (40,977)	$ 269,691
Net income (loss) per share attributable to Ambac Financial Group, Inc. common shareholders	$ (8.66)	$ 1.83	$ 2.36	$ 0.68
Basic	$ (8.66)	$ 1.77	$ 2.30	$ 0.65

Consolidated Statements of Tot5

Consolidated Statements of Total Comprehensive Income (Parenthetical) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Unrealized (loss) gain on securities, taxes	$ 0	$ 0	$ 0	$ 0
Gain (loss) on foreign currency translation, taxes	0	0	0	0
Amortization of postretirement benefit, taxes	$ 0	$ 0	$ 0	$ 0

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - Successor [Member] - USD ($) $ in Thousands	Total	Retained Earnings/Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Common Stock Held in Treasury, at Cost [Member]	Noncontrolling Interest [Member]
Beginning balance at Dec. 31, 2013	$ 978,423	$ 505,219	$ 11,661	$ 0	$ 450	$ 185,673	$ (19)	$ 275,439
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	269,292	30,487	239,204	0	0	0	0	(399)
Stock-based compensation	2,960	0	0	0	0	2,960	0	0
Warrants Purchased During Period Dollars	0
Proceeds from warrant exercises	15	0	0	0	0	15	0	0
Ending balance at Sep. 30, 2014	1,250,690	535,706	250,865	0	450	188,648	(19)	275,040
Beginning balance at Dec. 31, 2014	1,673,735	989,290	220,283	0	450	189,138	(56)	274,630
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	(41,578)	106,419	(147,396)	0	0	0	0	(601)
Stock-based compensation	2,150	0	0	0	0	2,150	0	0
Stock Issued During Period, Value, Share-based Compensation, Gross	(256)	(56)					(200)
Warrants Purchased During Period Dollars	(5,017)	(3,707)				(1,310)
Proceeds from warrant exercises	3	0	0	0	0	3	0	0
Ending balance at Sep. 30, 2015	$ 1,629,037	$ 1,091,946	$ 72,887	$ 0	$ 450	$ 189,981	$ (256)	$ 274,029

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - Successor [Member] - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flows from operating activities:
Net income (loss) attributable to common shareholders	$ 106,419	$ 30,487
Net (loss) gain	401	242
Net income (loss)	106,018	30,245
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	2,136	2,223
Goodwill, Impairment Loss	514,511	0
Amortization of bond premium and discount	(99,534)	(50,432)
Reorganization items	0	211
Share-based compensation	2,150	2,960
Deferred income taxes	(122)	(23)
Current income taxes	(6,686)	47
Unearned premiums, net	(227,952)	(284,355)
Losses and loss expenses, net	(422,892)	59,741
Ceded premiums payable	(2,785)	(9,858)
Investment income due and accrued	(98)	4,845
Premium receivables	105,161	186,389
Accrued interest payable	30,860	81,956
Amortization of insurance intangible assets	115,200	109,878
Net mark-to-market (gains) losses	(42,227)	(11,491)
Net realized investment gains	$ (50,854)	(29,401)
Financial Guarantee Insurance Contracts, Premium Received over Contract Period, Premium Receivable, Weighted Average Collection Period	9 years 8 months 12 days
Other-than-temporary impairment charges	$ 13,289	24,157
Net realized (gains) losses on extinguishment of debt	(81)	0
Variable interest entity activities	(38,130)	34,574
Other, net	82,944	106,703
Net cash provided by operating activities	80,908	258,369
Cash flows from investing activities:
Proceeds from sales of bonds	797,660	1,727,142
Proceeds from matured bonds	695,879	896,936
Purchases of bonds	(1,696,858)	(2,547,727)
Proceeds from sales of other invested assets	147,336	40,173
Purchases of other invested assets	(101,913)	(54,768)
Change in short-term investments	(4,715)	(279,781)
Loans, net	215	112
Change in swap collateral receivable	(17,032)	(105,354)
Other, net	(2,480)	6,553
Net cash (used in) investing activities	(181,908)	(316,714)
Cash flows from financing activities:
Proceeds from the sale of Junior Surplus Notes of the Segregated Account	0	224,262
Proceeds from Variable Interest Entity Secured Borrowing	144,189	0
Paydowns of a secured borrowing	(7,355)	0
Proceeds from warrant exercises	3	15
Warrants Purchased During Period Dollars	(5,017)	0
Payments for investment agreement draws	(63,872)	(199,970)
Payments for extinguishment of long-term debt	(13,752)	0
Net cash provided by financing activities	54,196	24,307
Net cash flow	(46,804)	(34,038)
Cash and cash equivalents at beginning of period	73,903	77,370
Cash and cash equivalents end of period	73,903	77,370
Supplemental disclosure of cash flow information:
Income taxes	15,176	3,246
Interest on secured borrowing	449	0
Interest on investment agreements	261	459
Cash payments related to reorganization items:
Professional fees paid for services rendered in connection with the Chapter 11 proceeding	$ 0	$ 272

Background and Business Descrip

Background and Business Description	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Background and Business Description	1. BACKGROUND AND BUSINESS DESCRIPTION Ambac Financial Group, Inc. (“Ambac” or the “Company”), headquartered in New York City, is a financial services holding company incorporated in the state of Delaware on April 29, 1991 . Ambac has two reportable business segments: Financial Guarantee and Financial Services. Ambac’s financial guarantee business segment is conducted through its primary operating subsidiary, Ambac Assurance Corporation (“Ambac Assurance”), and its wholly owned subsidiary, Ambac Assurance UK Limited (“Ambac UK”). Insurance policies issued by Ambac Assurance and Ambac UK generally guarantee payment when due of the principal and interest on the obligations guaranteed. Ambac Assurance also has another wholly-owned financial guarantee subsidiary, Everspan Financial Guarantee Corp. (“Everspan”), which has been in runoff since its acquisition in 1997. The deterioration of Ambac Assurance’s financial condition resulting from losses in its insured portfolio since 2007 has prevented Ambac Assurance from being able to write new business. An inability to write new business has and will continue to negatively impact Ambac’s future operations and financial results. Ambac Assurance’s ability to pay dividends and, as a result, Ambac’s liquidity, have been significantly restricted by the deterioration of Ambac Assurance’s financial condition, by the rehabilitation of the Segregated Account (as defined below) and by the terms of the Settlement Agreement, dated as of June 7, 2010 (the "Settlement Agreement"), by and among Ambac Assurance, Ambac Credit Products LLC (“ACP”), Ambac and certain counterparties to credit default swaps with ACP that were guaranteed by Ambac Assurance. Ambac Assurance is also restricted in its ability to pay dividends pursuant to regulatory restrictions, the terms of its Auction Market Preferred Shares, and the terms of agreements entered into with the Segregated Account. It is highly unlikely that Ambac Assurance will be able to make dividend payments to Ambac for the foreseeable future. Ambac’s financial services business segment is conducted through subsidiaries of Ambac Assurance, which provide financial and investment products, including investment agreements, funding conduits and interest rate swaps, principally to the clients of its financial guarantee business. Ambac Assurance insured all of the obligations of its financial services subsidiaries. These businesses are in active runoff, which is being effectuated by transaction terminations, settlements, and scheduled amortization of contracts. The Financial Services business also maintains interest rate derivatives to mitigate exposure to floating rate insured obligations in the Financial Guarantee segment. Ambac’s primary goal is to maximize shareholder value through executing the following key strategies: • Increasing the value of its investment in Ambac Assurance by actively managing its assets and liabilities with a focus on maximizing risk-adjusted investment portfolio returns and mitigating or remediating losses on poorly performing insured transactions through executing policy commutations, pursuing recoveries of losses through litigation and the exercise of contractual and legal rights, restructuring transactions, and other means; and • Selectively exploring opportunities to grow and diversify Ambac, which may include the development or acquisition of financial services businesses such as advisory, asset servicing, asset management and/or insurance. In October 2015, Ambac Assurance introduced a new program to invest in residential real estate owned (REO) properties from Ambac Assurance insured transactions. A main component of the value creation will be the result of making repairs to the REO properties in order to bring them up to neighborhood standards. Upon completion of necessary repairs, the properties will either be immediately re-sold or re-sold at a future date after being rented for a period of time. We are working with third-party vendors for necessary expertise and infrastructure related to this initiative. This program will be rolled out gradually in order to validate our internal investment thesis. Ambac Assurance is considering the possibility of entering into transactions whereby it would monetize certain assets and/or restructure or exchange certain outstanding debt and insurance obligations with the objective of ending the Segregated Account Rehabilitation Proceedings (as defined below). In furtherance of such transactions, Ambac Assurance has discussed with OCI (as defined below), and has from time to time discussed with several counterparty creditors, a potential exchange pursuant to which outstanding surplus notes (other than junior surplus notes) and Deferred Amounts (as defined below), including accrued interest, would be exchanged for new securities and/or cash. As of the date of this filing, Ambac Assurance has not reached any agreement on the terms of a potential exchange, and we cannot provide assurance that any such transaction will be entered into by Ambac Assurance in the future, or if it is, as to the timing, terms or conditions of any such transaction. Any such transaction would remain subject to the prior approval of the board of Ambac Assurance, OCI and potentially the Rehabilitation Court (as defined below). Although we are exploring new business opportunities for Ambac, no assurance can be given that we will be able to identify or execute the acquisition or development of any new business. In addition, there can be no assurance that we will be able to obtain the financial and other resources that may be required to finance the acquisition or development of any new business. Due to these factors, as well as uncertainties relating to the ability of Ambac Assurance to deliver value to Ambac, the value of our securities is speculative. The execution of Ambac’s strategy to increase the value of its investment in Ambac Assurance is subject to the authority of the Rehabilitator (as defined below) to control the management of the Segregated Account. In exercising such authority, the Rehabilitator will act for the benefit of policyholders, and will not take into account the interests of Ambac. Similarly, by operation of the contracts executed in connection with the establishment, and subsequent rehabilitation, of the Segregated Account, the Rehabilitator retains rights to oversee and approve certain actions taken by or in respect of Ambac Assurance. This oversight by the Rehabilitator could impair Ambac’s ability to execute certain of its strategies. Ambac Assurance's ability to commute policies or purchase certain investments may also be limited by available liquidity. As a result of uncertainties associated with the aforementioned oversight by the Rehabilitator of the Segregated Account, management has concluded that there is substantial doubt about Ambac's ability to continue as a going concern. Ambac’s financial statements as of and for the three and nine months ended September 30, 2015 and the year ended December 31, 2014 , respectively, are prepared assuming Ambac continues as a going concern and do not include any adjustment that might result from its inability to continue as a going concern. In March 2010, Ambac Assurance established a Segregated Account pursuant to Wisc. Stat. §611.24 (2) (the “Segregated Account”) to segregate certain segments of Ambac Assurance’s liabilities, and the Office of the Commissioner of Insurance for the State of Wisconsin (“OCI” (which term shall be understood to refer to such office as regulator of Ambac Assurance and to refer to the Commissioner of Insurance for the State of Wisconsin as rehabilitator of the Segregated Account (the “Rehabilitator”), as the context requires)) commenced rehabilitation proceedings in the Dane County, Wisconsin Circuit Court (the “Rehabilitation Court”) with respect to the Segregated Account (the “Segregated Account Rehabilitation Proceedings”) in order to permit OCI to facilitate an orderly run-off and/or settlement of the liabilities allocated to the Segregated Account pursuant to the provisions of the Wisconsin Insurers Rehabilitation and Liquidation Act. On October 8, 2010, OCI filed a plan of rehabilitation for the Segregated Account (the “Segregated Account Rehabilitation Plan”) in the Rehabilitation Court. On June 11, 2014, the Rehabilitation Court approved amendments to the Segregated Account Rehabilitation Plan that had been proposed by the Rehabilitator, and the Segregated Account Rehabilitation Plan, as amended, became effective on June 12, 2014. Under the amended Segregated Account Rehabilitation Plan holders of permitted policy claims have received and will receive an initial interim cash payment for a portion of each policy claim (“Interim Payment”), together with the right to receive a deferred payment equal to the balance of the unpaid policy claim, as may be adjusted from time to time pursuant to the terms of the amended Segregated Account Rehabilitation Plan (“Deferred Amount”). Net par exposure as of September 30, 2015 for policies allocated to the Segregated Account was $16,595,339 . Policy obligations not allocated to the Segregated Account remain in the General Account of Ambac Assurance, and such policies in the General Account are not subject to and, therefore, will not be directly impacted by the Segregated Account Rehabilitation Plan. To pay claims and other liabilities, the Segregated Account has the ability to demand payment from time to time under an aggregate excess of loss reinsurance agreement provided by Ambac Assurance (the “Reinsurance Agreement”). In addition, certain operating and administrative costs and expenses of the Segregated Account are reimbursable by Ambac Assurance pursuant to the Cooperation Agreement, dated as of March 24, 2010, by and between the Segregated Account and Ambac Assurance, as amended (the “Cooperation Agreement”). Ambac Assurance is not obligated to make payments under the Reinsurance Agreement or Cooperation Agreement if its surplus as regards to policyholders is less than $100,000 (the “Minimum Surplus Amount”). As long as the surplus as regards to policyholders is not less than the Minimum Surplus Amount, payments by Ambac Assurance to the Segregated Account under the Reinsurance Agreement and Cooperation Agreement are not capped. At September 30, 2015 , Ambac Assurance’s surplus as regards to policyholders of $350,559 exceeded the Minimum Surplus Amount. In the event that Ambac Assurance does not maintain surplus in excess of the Minimum Surplus Amount, the Segregated Account would experience a shortfall in funds available to pay its liabilities. Any such shortfall would be a consideration for the Rehabilitator in the determination of whether any changes to the Segregated Account Rehabilitation Plan (as defined above) and/or the amount of partial policy claim payments are necessary or appropriate or whether to institute general rehabilitation proceedings against Ambac Assurance.

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies (Notes)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block]	2. BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES The Company has disclosed its significant accounting policies in Note 2. Significant Accounting Policies in the Notes to Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 . The following significant accounting policies provide an update to those included in the Company’s Annual Report on Form 10-K. Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles ("GAAP") for interim financial reporting and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by GAAP for annual periods. These financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Annual Report on Form 10-K for the year ended December 31, 2014 . The accompanying consolidated financial statements have not been audited by an independent registered public accounting firm in accordance with the standards of the Public Company Accounting Oversight Board (U.S.), but in the opinion of management such financial statements include all adjustments, consisting only of normal recurring adjustments, necessary for the fair statement of the Company’s consolidated financial position and results of operations. All intercompany balances and transactions have been eliminated. The results of operations for the three and nine months ended September 30, 2015 may not be indicative of the results that may be expected for the year ending December 31, 2015 . The December 31, 2014 consolidated balance sheet was derived from audited financial statements. The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. As additional information becomes available or actual amounts become determinable, the recorded estimates are revised and reflected in operating results. Goodwill: At the Fresh Start Reporting Date, we revalued our assets and liabilities to current estimated fair value. The excess reorganization value which could not be attributed to the fair value of specific identified tangible and intangible assets ("fair value of net assets") was recorded as goodwill. Pursuant to the Intangibles - Goodwill and Other Topic of the ASC, goodwill is not amortized but is subject to annual impairment testing. We test goodwill for impairment as of October 1 st of each year. Goodwill is also tested more frequently if indicators of impairment exist for each reporting unit. The Company has an option to first assess qualitative factors, in their totality, to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform a goodwill impairment test. If the Company determines that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, then the Company is required to perform the goodwill impairment test. Alternatively, we may bypass this qualitative assessment and perform step one of the goodwill impairment test described below. Goodwill impairment is determined using a two-step approach. In step one of the goodwill impairment test, the fair value of a reporting unit is compared with its carrying amount, including goodwill. If the fair value is in excess of the carrying amount, including goodwill, the reporting unit’s goodwill is considered not to be impaired. If the carrying amount, including goodwill, of a reporting unit exceeds its fair value, the second step of the goodwill impairment test is performed to measure the amount of impairment loss, if any. In step two of the goodwill impairment test, the implied fair value of a reporting unit’s goodwill is compared with the carrying amount of that goodwill. The implied fair value of goodwill is determined in the same manner as the amount of goodwill recognized in a business combination and is defined as the excess of the fair value of a reporting unit over the fair value of the net assets of a reporting unit. If the carrying amount of goodwill exceeds its implied fair value, an impairment loss is recognized for the excess. If the carrying amount of goodwill is less than its implied fair value, no goodwill impairment is recognized. Goodwill impairment testing is performed at the reporting unit level. We have identified two reporting units of Ambac: (1) Financial Guarantee, which provides financial guarantees (including credit derivatives) for public finance, structured finance and other obligations; and (2) Financial Services, which provides investment agreements, funding conduits, and interest rate swaps, principally to clients of the financial guarantee business. These reporting units are also the sole operating segments which make up the Financial Guarantee and Financial Services reportable segments, respectively, as further described in Note 19. Segment Information in the Notes to Consolidated Financial Statements included Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 . We have assigned assets and liabilities to each reporting unit based on specific identification. In evaluating which reporting units should be assigned goodwill, we considered the sources of Ambac’s estimated enterprise value at the Fresh Start Reporting Date, as further described in Note 3. Fresh Start Financial Statement Reporting in the Notes to Consolidated Financial Statements included Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 . Based on that analysis, we have assigned all goodwill recorded at the Fresh Start Reporting Date to the Financial Guarantee reporting unit. During the September 30, 2015 reporting period, Ambac determined sufficient indicators of potential impairment existed to perform an interim goodwill impairment evaluation for the Financial Guarantee reporting unit. These indicators included the recent trading values of Ambac stock and changes in Ambac credit spreads. In conducting the goodwill impairment analysis as of September 30, 2015 , we performed step one of the goodwill impairment test for the Financial Guarantee reporting unit. We estimated the fair value of the Financial Guarantee reporting unit using a market approach, which is derived using: i) Ambac’s common stock and warrant market capitalization, ii) fair value estimates of Ambac Assurance preferred shares (reported as noncontrolling interests on Ambac's balance sheet) and iii) an estimated control premium. Step one of the impairment test indicated the Financial Guarantee reporting unit's carrying value exceeded its fair value. Accordingly, the Company performed step two of the impairment test as of September 30, 2015 , which indicated the implied fair value of goodwill was zero. This was the result of substantial decreases in the Financial Guarantee reporting unit's fair value and substantial increases in the fair value of its net assets. The fair value of the Financial Guarantee reporting unit decreased significantly due to a material decrease in Ambac's market capitalization components (described above). The Financial Guarantee reporting unit's fair value of net assets increased significantly primarily as a result of a decrease in the estimated fair value of financial guarantee liabilities and, to a lesser extent, a decrease in the fair value of long-term debt. The fair value decrease in financial guarantee liabilities, which is a Level 3 estimate, was primarily driven by wider Ambac credit spreads and positive loss and loss expense reserves development. Please refer to Note 7. Fair Value Measurements for further discussion on the fair value model for financial guarantee liabilities. The fair value decrease in long-term debt was driven by lower market pricing on surplus notes and junior surplus notes. As a result, the Company recorded a full non-cash, non-tax deductible goodwill impairment charge of $514,511 million at September 30, 2015. The following is a summary of activity in goodwill for the Financial Guarantee reporting unit: Nine Months Ended September 30, 2015 Year Ended December 31, 2014 Beginning balance $ 514,511 $ 514,511 Impairment loss (514,511 ) — Ending balance $ — $ 514,511 Reclassifications Certain reclassifications have been made to prior years' amounts to conform to the current year's presentation. Recently Adopted and Recently Issued Accounting Standards Adopted: Effective January 1, 2015, Ambac adopted ASU 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360) - Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity . The objective of this ASU is to limit discontinued operations reporting to disposals of components of an entity that represent strategic shifts that have (or will have) a major effect on an entity's operations and financial results. Under previous U.S. GAAP, many disposals, some of which may be routine in nature and not a change in an entity's strategy, were reported in discontinued operations. The ASU also requires certain expanded disclosures for discontinued operations and disclosure of the pre-tax profit or loss of an individually significant component of an entity that does not qualify for discontinued operations reporting. The adoption of this ASU did not have a material effect on Ambac's financial statements. Issued: In April 2015, the FASB issued ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30) . This ASU simplifies the presentation of debt issuance costs by requiring that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs are not affected by the amendments in this ASU. The ASU is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Early adoption is also permitted for financial statements that have not been previously issued. Upon adoption, the ASU must be retrospectively applied to all prior periods presented. Ambac has not determined whether it will adopt ASU 2015-03 prior to January 1, 2016. The adoption of this ASU is not expected to have a material impact on Ambac's financial statements. In May 2015, the FASB issued ASU 2015-07, Fair Value Measurement (Topic 820) - Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent) . Reporting entities are permitted to use net asset value ("NAV") as a practical expedient to measure the fair value of certain investments. Under current U.S. GAAP, investments that use the NAV practical expedient to measure fair value are categorized within the fair value hierarchy as level 2 or level 3 investments depending on their redemption attributes, which has led to diversity in practice. This ASU will remove the requirement to categorize within the fair value hierarchy all investments that use the NAV practical expedient for fair value measurement purposes. Furthermore, the ASU will remove the requirement to make certain disclosures for all investments that are eligible to be measured at fair value using the NAV practical expedient. The ASU is effective for fiscal years beginning after December 15, 2015 and interim periods with those fiscal years. The ASU must be applied retrospectively to all prior periods presented. Ambac will adopt ASU 2015-07 on January 1, 2016. The adoption of this ASU is not expected to have a material impact on Ambac's financial statements. In May 2015, the FASB issued ASC 2015-09, Financial Services - Insurance (Topic 944) - Disclosures about Short-Duration Contracts. The primary objective of this ASU is to improve disclosures for insurance entities which issue short-duration contracts. The ASU made significant amendments to the Short-Duration Contract disclosure section and limited amendments affecting the General disclosure section of Topic 944. Ambac, as a provider of financial guarantee contracts, is subject to the General sections but not the Short-Duration Contract sections of Topic 944. The limited amendments made to the General disclosure section are not expected to have a material impact on Ambac's financial statement disclosures. The ASU is effective for annual periods beginning after December 15, 2015, and interim periods within annual periods beginning after December 15, 2016. Ambac will adopt ASU 2015-09 on December 31, 2016.

Special Purpose Entities, Inclu

Special Purpose Entities, Including Variable Interest Entities	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Special Purpose Entities, Including Variable Interest Entities	3. SPECIAL PURPOSE ENTITIES, INCLUDING VARIABLE INTEREST ENTITIES ("VIEs") Ambac, with its subsidiaries, has engaged in transactions with special purpose entities, including VIEs, in various capacities. Ambac most commonly provides financial guarantees, including credit derivative contracts, for various debt obligations issued by special purpose entities, including VIEs. Ambac has also sponsored certain special purpose entities to fund the purchase of certain financial assets. Ambac is also an investor in collateralized debt obligations, mortgage-backed and other asset-backed securities issued by VIEs and its ownership interest is generally insignificant to the VIE and/or Ambac does not have rights that direct the activities that are most significant to such VIE. Financial Guarantees: Ambac’s subsidiaries provide financial guarantees in respect of assets held or debt obligations of special purpose entities, including VIEs. Ambac’s primary variable interest exists through this financial guarantee insurance or credit derivative contract. The transaction structures provide certain financial protection to Ambac. This financial protection can take several forms; however, the most common are over-collateralization, first loss and excess spread. In the case of over-collateralization (i.e., the principal amount of the securitized assets exceeds the principal amount of the debt obligations guaranteed), the structure allows the transaction to experience defaults among the securitized assets before a default is experienced on the debt obligations that have been guaranteed by Ambac’s subsidiaries. In the case of first loss, the financial guarantee insurance policy or credit derivative contract only covers a senior layer of losses on assets held or debt issued by special purpose entities, including VIEs. The first loss with respect to the assets is either retained by the asset seller or sold off in the form of equity or mezzanine debt to other investors. In the case of excess spread, the securitized assets contributed to special purpose entities, including VIEs, generate interest cash flows that are in excess of the interest payments on the related debt; such excess cash flow is applied to redeem debt, thus creating over-collateralization. Generally, upon deterioration in the performance of a transaction or upon an event of default as specified in the transaction legal documents, Ambac will obtain certain loss remediation rights. These rights may enable Ambac to direct the activities of the entity that most significantly impact the entity’s economic performance. We determined that Ambac’s subsidiaries generally have the obligation to absorb a VIE's expected losses given that they have issued financial guarantees supporting the liabilities (and in certain cases assets). As further described below, we consolidated certain VIEs because: (i) we determined for certain transactions that experienced the aforementioned performance deterioration, that Ambac’s subsidiaries had the power, through voting rights or similar rights, to direct the activities of certain VIEs that most significantly impact the VIE’s economic performance because certain triggers had been breached in these transactions resulting in their ability to exercise certain loss remediation activities, or (ii) due to the passive nature of the VIEs’ activities, Ambac’s subsidiaries’ contingent loss remediation rights upon a breach of certain triggers in the future is considered to be the power to direct the activities that most significantly impact the VIEs’ economic performance. With respect to VIEs involving Ambac financial guarantees, Ambac is required to consolidate a VIE in the period that applicable triggers result in Ambac having control over the VIE’s most significant economic activities. A VIE is deconsolidated in the period that Ambac no longer has such control, which could occur in connection with insurance policies that are allocated to the Segregated Account, execution of remediation activities on the transaction or amortization of insured exposure, any of which may reduce the degree of Ambac’s control over a VIE. Assets and liabilities of VIEs that are consolidated as a result of Ambac's variable interest arising from financial guarantees written by Ambac's subsidiaries are reported within Variable interest entity assets or Variable interest entity liabilities on the Consolidated Balance Sheets. Results from such VIEs are reported within Income (loss) on variable interest entities in the Consolidated Statements of Total Comprehensive Income. Ambac Sponsored VIEs: A subsidiary of Ambac transferred financial assets to two special purpose entities. The business purpose of these entities was to provide certain financial guarantee clients with funding for their debt obligations. These special purpose entities were established as separate legal entities, demonstrably distinct from Ambac and that Ambac, its affiliates or its agents could not unilaterally dissolve. The permitted activities of these entities were contractually limited to purchasing assets from Ambac, issuing MTNs to fund such purchase, executing derivative hedges and obtaining financial guarantee policies with respect to indebtedness incurred. Effective February 17, 2015, one of the special purpose entities was liquidated as it no longer had any outstanding liabilities. Ambac has not consolidated these entities because Ambac Assurance’s policies issued to these entities were allocated to the Segregated Account, thereby limiting Ambac’s control over the entities’ most significant economic activities. Ambac elected to account for its equity interest in these entities at fair value under the fair value option in accordance with the Financial Instruments Topic of the ASC. We believe that the fair value of the investments in these entities provides for greater transparency for recording profit or loss as compared to the equity method under the Investments – Equity Method and Joint Ventures Topic of the ASC. Refer to Note 7. Fair Value Measurements for further information on the valuation technique and inputs used to measure the fair value of Ambac’s equity interest in these entities. At September 30, 2015 and December 31, 2014 the fair value of these entities are $9,322 and $12,036 , respectively, and is reported within Other assets on the Consolidated Balance Sheets. • Since their inception, there have been 15 individual transactions with these entities, of which 3 transactions remain outstanding as of September 30, 2015 . Total principal amount of debt outstanding was $457,960 and $457,960 at September 30, 2015 and December 31, 2014 , respectively. In each case, Ambac sold assets to these entities. The assets are composed of utility obligations with a weighted average rating of BBB at September 30, 2015 and weighted average life of 6.8 years . The purchase by these entities of financial assets was financed through the issuance of medium-term notes (“MTNs”), which are cross-collateralized by the purchased assets. The MTNs have the same expected weighted average life as the purchased assets. Derivative contracts (interest rate swaps) are used within the entities for economic hedging purposes only. Derivative positions were established at the time MTNs were issued to purchase financial assets. As of September 30, 2015 Ambac Assurance had financial guarantee insurance policies issued for all assets, MTNs and derivative contracts owned and outstanding by the entities. • Insurance premiums paid to Ambac Assurance by these entities are earned in a manner consistent with other insurance policies, over the risk period. Additionally, any losses incurred on such insurance policies are included in Ambac’s Consolidated Statements of Total Comprehensive Income (Loss). Under the terms of an Administrative Agency Agreement, Ambac provides certain administrative duties, primarily collecting amounts due on the obligations and making interest payments on the MTNs. In July 2015, Ambac Assurance entered into a secured borrowing transaction whereby it sold 17 Ambac insured residential mortgage-backed securities (the "Securities") and all rights associated therewith as of May 31, 2015, to a Delaware statutory trust (the "Trust") in exchange for an equity certificate in the Trust, all financial guarantee claim payments associated with the Securities and cash of $146,000 (prior to expenses associated with the transaction). The Securities had par and fair value of $386,129 and $403,106 as of September 30, 2015 , respectively. Although the Securities were legally sold to the Trust, the Securities will remain in Invested assets on the Consolidated Balance Sheets. Refer to Note 8. Investments for further discussion of the restrictions on the invested assets. At the same time, a second Delaware statutory trust (the "Issuer"), issued $146,000 of debt securities and used the proceeds, together with an equity certificate of the Issuer, to purchase from the Trust a certificate entitling the Issuer to, and secured by, all principal and interest payments (other than financial guarantee claim payments) on the Securities. Interest on the debt securities is payable monthly at an annual rate of one month LIBOR + 2.8% . Both the Trust and the Issuer are consolidated VIEs because Ambac Assurance was involved in their design and holds a significant amount of the beneficial interests issued by the VIEs or guaranteed the assets held by the VIEs. VIE debt outstanding to third parties under this secured borrowing transaction had a carrying value of $137,049 as of September 30, 2015 and is reported in Long-Term Debt on the Consolidated Balance Sheets. Consolidation of VIEs: Upon initial consolidation of a VIE, we recognize a gain or loss in earnings for the difference between: (i) the fair value of the consideration paid (when applicable), the fair value of any non-controlling interests and the reported amount of any previously held interests and (ii) the net amount, as measured on a fair value basis, of the assets and liabilities consolidated. Upon deconsolidation of a VIE, we recognize a gain or loss for the difference between: (i) the fair value of any consideration received (when applicable), the fair value of any retained non-controlling investment in the VIE and the carrying amount of any non-controlling interest in the VIE and (ii) the carrying amount of the VIE’s assets and liabilities. Gains or losses from consolidation and deconsolidation that are reported in earnings are reported within Income (loss) on variable interest entities on the Consolidated Statements of Total Comprehensive Income (Loss). The variable interest in a VIE generally involves one or more of the following: a financial guarantee policy issued to the VIE, a written credit derivative contract that references liabilities of the VIE or an investment in securities issued by the VIE. The impact of consolidating such VIEs on Ambac’s balance sheet is the elimination of transactions between the consolidated VIEs and Ambac’s operating subsidiaries and the inclusion of the VIE’s third party assets and liabilities. For a financial guarantee insurance policy issued to a consolidated VIE, Ambac does not reflect the financial guarantee insurance policy in accordance with the related insurance accounting rules under the Financial Services – Insurance Topic of the ASC. Consequently, upon consolidation, Ambac eliminates the insurance assets and liabilities associated with the policy from the Consolidated Balance Sheets. Such insurance assets and liabilities may include premium receivables, reinsurance recoverable, deferred ceded premium, subrogation recoverable, unearned premiums, loss and loss expense reserves, ceded premiums payable and insurance intangible assets. Furthermore, with respect to the consolidation or deconsolidation of VIEs related to financial guarantee insurance policies, there typically is no consideration paid or received by Ambac, and consequently has no impact on the above described gain or loss calculation. For investment securities owned by Ambac that are debt instruments issued by the VIE, the investment securities balance is eliminated upon consolidation. Ambac did not consolidate any VIEs solely as a result of purchases of the VIE’s debt instruments for any of the periods presented. As of September 30, 2015 consolidated VIE assets and liabilities relating to 15 consolidated entities were $14,875,442 and $14,830,828 , respectively. As of December 31, 2014 , consolidated VIE assets and liabilities relating to 15 consolidated entities were $15,126,110 and $15,085,685 , respectively. Ambac is not primarily liable for, and does not guarantee all of the debt obligations issued by the VIEs. Ambac would only be required to make payments on the VIE debt obligations in the event that the issuer of such debt obligations defaults on any principal or interest due and such obligation is guaranteed by Ambac. Additionally, Ambac’s general creditors, other than those specific policy holders which own the VIE debt obligations, do not have rights with regard to the assets of the VIEs. Ambac evaluates the net income effects and earnings per share effects to determine attributions between Ambac and non-controlling interests as a result of consolidating a VIE. Ambac has determined that the net changes in fair value of most consolidated VIE assets and liabilities are attributable to Ambac’s interests through financial guarantee premium and loss payments with the VIE. The financial reports of certain VIEs are prepared by outside trustees and are not available within the time constraints Ambac requires to ensure the financial accuracy of the operating results. As such, the financial results of certain VIEs are consolidated on a time lag that is no longer than 90 days. The table below provides the fair value of fixed income securities, by asset-type, held by consolidated VIEs as of September 30, 2015 and December 31, 2014 : September 30, December 31, Investments: Corporate obligations $ 2,679,895 $ 2,743,050 Total variable interest entity assets: fixed income securities $ 2,679,895 $ 2,743,050 The following table provides supplemental information about the loans held as assets and long-term debt associated with the VIEs for which the fair value option has been elected as of September 30, 2015 and December 31, 2014 : Estimated fair value Unpaid principal balance September 30, 2015 Loans $ 12,183,061 $ 9,446,235 Long-term debt 12,791,012 11,366,061 December 31, 2014 Loans 12,371,177 10,236,695 Long-term debt $ 12,882,076 $ 11,925,499 For the three months ended September 30, 2015 , Ambac deconsolidated one VIE as a result of the termination of the associated financial guarantee policy. There was a gain of $572 reported in Income (loss) on variable interest entities on the Consolidated Statements of Total Comprehensive Income (Loss). For the nine months ended September 30, 2015 , Ambac deconsolidated two VIE's; one as a result of the termination of the associated financial guarantee policy and one as a result of the associated financial guarantee exposure matured. There was a gain of $572 reported in Income (loss) on variable interest entities on the Consolidated Statements of Total Comprehensive Income (Loss). Variable Interests in Non-Consolidated VIEs As further described in Note 1. Background and Business Description in the Notes to Consolidated Financial Statements included Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 , on August 28, 2014, Ambac monetized its ownership of the junior surplus note issued to it by the Segregated Account by depositing the junior surplus note into a newly formed VIE trust in exchange for cash and an owner trust certificate, which represents Ambac's right to residual cash flows from the junior surplus note. Ambac does not consolidate the VIE. Ambac reports its interest in the VIE as an equity investment within Other investments on the Consolidated Balance Sheets with associated results from operations included within Net investment income: Other investments on the Consolidated Statements of Total Comprehensive Income (Loss). The following table displays the carrying amount of the assets, liabilities and maximum exposure to loss of Ambac’s variable interests in non-consolidated VIEs resulting from financial guarantee and derivative contracts by major underlying asset classes, as of September 30, 2015 and December 31, 2014 : Carrying Value of Assets and Liabilities Maximum (1) Insurance (2) Insurance (3) Net Derivative (4) September 30, 2015: Global structured finance: Collateralized debt obligations $ 1,041,843 $ 271 $ 3,716 $ (139,859 ) Mortgage-backed—residential 17,722,719 1,034,921 2,740,222 — Other consumer asset-backed 4,321,282 51,802 648,958 (349 ) Other commercial asset-backed 2,597,067 115,751 105,826 — Other 3,308,329 82,160 484,964 16,006 Total global structured finance 28,991,240 1,284,905 3,983,686 (124,202 ) Global public finance 30,463,734 427,717 483,506 (21,421 ) Total $ 59,454,974 $ 1,712,622 $ 4,467,192 $ (145,623 ) December 31, 2014: Global structured finance: Collateralized debt obligations $ 1,386,100 $ 345 $ 4,000 $ (145,565 ) Mortgage-backed—residential 19,464,549 1,011,888 2,924,987 — Other consumer asset-backed 5,109,776 65,204 885,572 (36,877 ) Other commercial asset-backed 3,119,891 135,215 128,988 — Other 3,801,382 97,345 599,915 18,176 Total global structured finance 32,881,698 1,309,997 4,543,462 (164,266 ) Global public finance 31,639,004 457,774 533,192 (22,135 ) Total $ 64,520,702 $ 1,767,771 $ 5,076,654 $ (186,401 ) (1) Maximum exposure to loss represents the maximum future payments of principal and interest on insured obligations and derivative contracts plus Deferred Amounts and accrued and unpaid interest thereon. Ambac’s maximum exposure to loss does not include the benefit of any financial instruments (such as reinsurance or hedge contracts) that Ambac may utilize to mitigate the risks associated with these variable interests. (2) Insurance assets represent the amount recorded in “Premium receivables” and “Subrogation recoverable” for financial guarantee contracts on Ambac’s Consolidated Balance Sheets. (3) Insurance liabilities represent the amount recorded in “Loss and loss expense reserves” and “Unearned premiums” for financial guarantee contracts on Ambac’s Consolidated Balance Sheets. (4) Net derivative assets (liabilities) represent the fair value recognized on credit derivative contracts and interest rate swaps on Ambac’s Consolidated Balance Sheets.

Comprehensive Income

Comprehensive Income	9 Months Ended
	Sep. 30, 2015
Equity [Abstract]
Comprehensive Income	4. COMPREHENSIVE INCOME The following tables detail the changes in the balances of each component of accumulated other comprehensive income for the affected periods: Unrealized Gains (1) Amortization of (1) Gain (Loss) on (1) Total Three Months Ended September 30, 2015 Beginning Balance $ 79,406 $ 9,784 $ 6,172 $ 95,362 Other comprehensive income before reclassifications 1,342 — (30,637 ) (29,295 ) Amounts reclassified from accumulated other comprehensive income 7,040 (220 ) — 6,820 Net current period other comprehensive income (loss) 8,382 (220 ) (30,637 ) (22,475 ) Balance at September 30, 2015 $ 87,788 $ 9,564 $ (24,465 ) $ 72,887 Three Months Ended September 30, 2014 Beginning Balance $ 231,975 $ 10,439 $ 63,914 $ 306,328 Other comprehensive income before reclassifications (12,222 ) — (38,034 ) (50,256 ) Amounts reclassified from accumulated other comprehensive income (5,003 ) (204 ) — (5,207 ) Net current period other comprehensive income (loss) (17,225 ) (204 ) (38,034 ) (55,463 ) Balance at September 30, 2014 $ 214,750 $ 10,235 $ 25,880 $ 250,865 (1) All amounts are net of tax and noncontrolling interest. Amounts in parentheses indicate debits. Unrealized Gains (1) Amortization of (1) Gain (Loss) on (1) Total Nine Months Ended September 30, 2015: Beginning Balance $ 210,693 $ 10,031 $ (441 ) $ 220,283 Other comprehensive income before reclassifications (85,313 ) — (24,024 ) (109,337 ) Amounts reclassified from accumulated other comprehensive income (37,592 ) (467 ) — (38,059 ) Net current period other comprehensive income (loss) (122,905 ) (467 ) (24,024 ) (147,396 ) Balance at September 30, 2015 $ 87,788 $ 9,564 $ (24,465 ) $ 72,887 Nine Months Ended September 30, 2014: Beginning Balance $ (41,910 ) $ 10,847 $ 42,724 $ 11,661 Other comprehensive income before reclassifications 261,879 — (16,844 ) 245,035 Amounts reclassified from accumulated other comprehensive income (5,219 ) (612 ) — (5,831 ) Net current period other comprehensive income (loss) 256,660 (612 ) (16,844 ) 239,204 Balance at September 30, 2014 $ 214,750 $ 10,235 $ 25,880 $ 250,865 (1) All amounts are net of tax and noncontrolling interest. Amounts in parentheses indicate debits. The following table details the significant amounts reclassified from each component of accumulated other comprehensive income for the affected periods: Amount Reclassified from Accumulated (1) Affected Line Item in the Details about Accumulated Other Three Months Ended September 30, Consolidated Statement of Comprehensive Income Components 2015 2014 Total Comprehensive Income Unrealized Gains (Losses) on Available-for-Sale Securities $ 7,040 $ (5,003 ) Net realized investment (losses) gains — — Tax (expense) benefit $ 7,040 $ (5,003 ) Net of tax and noncontrolling interest (3) Amortization of Postretirement Benefit Prior service cost $ (167 ) $ (166 ) Underwriting and operating expenses (2) Actuarial gains (losses) (53 ) (38 ) Underwriting and operating expenses (2) (220 ) (204 ) Total before tax — — Tax (expense) benefit $ (220 ) $ (204 ) Net of tax and noncontrolling interest (3) Total reclassifications for the period $ 6,820 $ (5,207 ) Net of tax and noncontrolling interest (3) (1) Amounts in parentheses indicate debits to the Consolidated Statement of Total Comprehensive Income. (2) These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. (3) Amount agrees w ith amount reported as reclassifications from AOCI in the disclosure about changes in AOCI balances. Amount Reclassified from Accumulated (1) Affected Line Item in the Details about Accumulated Other Nine Months Ended September 30, Consolidated Statement of Comprehensive Income Components 2015 2014 Total Comprehensive Income Unrealized Gains (Losses) on Available-for-Sale Securities $ (37,592 ) $ (5,219 ) Net realized investment gains — — Tax (expense) benefit $ (37,592 ) $ (5,219 ) Net of tax and noncontrolling interest (3) Amortization of Postretirement Benefit Prior service cost $ (500 ) $ (498 ) Underwriting and operating expenses (2) Actuarial gains (losses) 33 (114 ) Underwriting and operating expenses (2) (467 ) (612 ) Total before tax — — Tax (expense) benefit $ (467 ) $ (612 ) Net of tax and noncontrolling interest (3) Total reclassifications for the period $ (38,059 ) $ (5,831 ) Net of tax and noncontrolling interest (3) (1) Amounts in parentheses indicate debits to the Consolidated Statement of Total Comprehensive Income. (2) These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. (3) Amount agrees w ith amount reported as reclassifications from AOCI in the disclosure about changes in AOCI balances.

Net Income Per Share

Net Income Per Share	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Net Income Per Share	5. NET INCOME PER SHARE Pursuant to the Second Modified Fifth Amended Plan of Reorganization of Ambac (the "Reorganization Plan"), 45,000,000 shares of new common stock at par value of $0.01 per share and 5,047,138 warrants were issued. Warrants entitle such holders to acquire up to 5,047,138 shares of new common stock at an exercise price of $16.67 per share at any time on or prior to April 30, 2023 . For the nine months ended September 30, 2015 and 2014 , 740 and 949 warrants were exercised, respectively, resulting in an issuance of 236 and 949 shares of common stock, respectively. On June 30, 2015, the Board of Directors of Ambac authorized the establishment of a warrant repurchase program that permits the repurchase of up to $10,000 of warrants. As of September 30, 2015 , Ambac had repurchased 577,500 warrants totaling $5,017 , leaving 4,461,637 warrants outstanding with an exercise price of $16.67 per share and expiration of April 30, 2023 . Basic net income per share is computed by dividing net income attributable to common shareholders by the weighted-average number of common shares outstanding and vested restricted stock units. Diluted net income per share is computed by dividing net income attributable to common shareholders by the weighted-average number of common shares used for basic earnings per share plus all potential dilutive common shares outstanding during the period. All potential dilutive common shares outstanding consider common stock deliverable pursuant to warrants issued under the Reorganization Plan and vested and unvested options, unvested restricted stock units and performance stock units granted under employee and director compensation plans. The following table provides a reconciliation of the common shares used for basic net income per share to the diluted shares used for diluted net income per share: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Basic weighted average shares outstanding 45,174,521 45,115,882 45,173,671 45,083,831 Effect of potential dilutive shares: Warrants — 1,469,203 1,154,313 1,892,211 Stock options — 8,220 7,083 10,569 Restricted stock units — 31,384 14,418 40,473 Performance stock units — — 2,729 — Diluted weighted average shares outstanding 45,174,521 46,624,689 46,352,214 47,027,084 For the three months ended September 30, 2015 , Ambac incurred net losses and accordingly excluded all potentially dilutive securities from the determination of diluted loss per share as their impact was antidilutive. Antidilutive securities for the three months ended September 30, 2015 included stock options and warrants to purchase 176,668 and 4,461,637 shares of common stock, respectively, where the exercise price was greater than the average market price, 78,460 restricted stock units and 96,349 performance stock units at their target amounts. Antidilutive securities for the nine months ended September 30, 2015 included stock options to purchase 110,000 shares of common stock where the exercise price was greater than the average market price.

Financial Guarantee Insurance C

Financial Guarantee Insurance Contracts	9 Months Ended
	Sep. 30, 2015
Insurance [Abstract]
Financial Guarantee Insurance Contracts	6. FINANCIAL GUARNTEE INSURANCE CONTRACTS Amounts presented in this Note relate only to Ambac’s non-derivative insurance business for insurance policies issued to beneficiaries, including VIEs, for which we do not consolidate the VIE. Net Premiums Earned: Gross premiums are received either upfront (typical of public finance obligations) or in installments (typical of structured finance obligations). For premiums received upfront, an unearned premium revenue (“UPR”) liability is established, which is initially recorded as the cash amount received. For installment premium transactions, a premium receivable asset and offsetting UPR liability is initially established in an amount equal to: (i) the present value of future contractual premiums due (the “contractual” method) or (ii) if the underlying insured obligation is a homogenous pool of assets which are contractually prepayable, the present value of premiums to be collected over the expected life of the transaction (the “expected” method). An appropriate risk-free rate corresponding to the weighted average life of each policy and currency is used to discount the future premiums contractually due or expected to be collected. For example, U.S. dollar exposures are discounted using U.S. Treasury rates while exposures denominated in a foreign currency are discounted using the appropriate risk-free rate for the respective currency. The weighted average risk-free rate at September 30, 2015 and December 31, 2014 , was 2.7% and 2.7% , respectively, and the weighted average period of future premiums used to estimate the premium receivable at September 30, 2015 and December 31, 2014 , was 9.7 years and 10.1 years, respectively. Insured obligations consisting of homogeneous pools for which Ambac uses expected future premiums to estimate the premium receivable and UPR include residential mortgage-backed securities. As prepayment assumptions change for homogenous pool transactions, or if there is an actual prepayment for a “contractual” method installment transaction, the related premium receivable and UPR are adjusted in equal and offsetting amounts with no immediate effect on earnings using new premium cash flows and the then current risk-free rate. Generally, the priority for the payment of financial guarantee premiums to Ambac, as required by the bond indentures of the insured obligations, is senior in the waterfall. Additionally, in connection with the allocation of certain liabilities to the Segregated Account, trustees and other parties are required under the Segregated Account Rehabilitation Plan and related court orders to continue to pay installment premiums, notwithstanding the Segregated Account Rehabilitation Proceedings. In evaluating the credit quality of the premium receivables, management evaluates the transaction waterfall structures and the internal ratings of the transactions underlying the premium receivables. Uncollectable premiums are determined on a policy basis and utilize a combination of historical premium collection data in addition to cash flow analysis to determine if an impairment in the related policy's premium receivables exist. As of September 30, 2015 and December 31, 2014 , approximately 28% and 32% of the premium receivables related to transactions with non-investment grade internal ratings, comprised mainly of non-investment grade RMBS, lease securitizations and student loan transactions, which comprised 7% , 6% , and 5% , of the total premium receivables at September 30, 2015 and 7% , 6% , and 8% of the total premium receivables at December 31, 2014 , respectively. At September 30, 2015 and December 31, 2014 , $15,802 and $17,780 respectively, of premium receivables were deemed uncollectable. Past due premiums on policies insuring non-investment grade obligations amounted to less than $500 at September 30, 2015 . Below is the gross premium receivable roll-forward (direct and assumed contracts) for the affected periods: Nine Months Ended September 30, 2015 2014 Beginning premium receivable $ 1,000,607 $ 1,453,021 Premium receipts (70,940 ) (100,646 ) Adjustments for changes in expected and contractual cash flows (39,613 ) (93,795 ) Accretion of premium receivable discount 18,795 29,644 Changes to uncollectable premiums 1,978 (801 ) Other adjustments (including foreign exchange) (15,381 ) (20,791 ) Ending premium receivable $ 895,446 $ 1,266,632 Similar to gross premiums, premiums ceded to reinsurers are paid either upfront or in installments. Premiums ceded to reinsurers reduce the amount of premiums earned by Ambac from its financial guarantee insurance policies. When a bond issue insured by Ambac Assurance has been retired, including those retirements due to calls, any remaining UPR is recognized at that time to the extent the financial guarantee contract is legally extinguished, causing accelerated premium revenue. For installment premium paying transactions, the recognition of any remaining UPR is offset by the reduction of the related premium receivable to zero (as it will not be collected as a result of the retirement), which may cause negative accelerated premium revenue. Ambac’s accelerated premium revenue for retired obligations for the three and nine months ended September 30, 2015 was $28,369 and $64,862 , and for the three and nine months ended September 30, 2014 was $9,192 and $42,296 , respectively. Certain obligations insured by Ambac have been legally defeased whereby government securities are purchased by the issuer with the proceeds of a new bond issuance, or less frequently with other funds of the issuer, and held in escrow. The principal and interest received from the escrowed securities are then used to retire the Ambac-insured obligations at a future date either to their maturity date (a refunding) or a specified call date (a pre-refunding). Ambac has evaluated the provisions in certain financial guarantee insurance policies issued on legally defeased obligations and determined those insurance policies have not been legally extinguished. For policies with refunding securities, premium revenue recognition is not impacted as the escrowed maturity date is the same as the previous legal maturity date. For policies with pre-refunding securities, the maturity date of the pre-refunded security has been shortened from its previous legal maturity. Although premium revenue recognition has not been accelerated in the period of the pre-refunding, it results in an increase in the rate at which the policy's remaining UPR is to be recognized. The effect of reinsurance on premiums written and earned for the respective periods was as follows: Three Months Ended September 30, 2015 Three Months Ended September 30, 2014 Written Earned Written Earned Direct $ (8,710 ) $ 77,982 $ (13,700 ) $ 68,685 Assumed — 22 — 23 Ceded (105 ) 6,469 (2,805 ) 3,877 Net premiums $ (8,605 ) $ 71,535 $ (10,895 ) $ 64,831 Nine Months Ended September 30, 2015 Nine Months Ended September 30, 2014 Written Earned Written Earned Direct $ (18,840 ) $ 214,787 $ (64,952 ) $ 222,894 Assumed — 66 — 114 Ceded (882 ) 16,721 (7,316 ) 10,617 Net premiums $ (17,958 ) $ 198,132 $ (57,636 ) $ 212,391 The table below summarizes the future gross undiscounted premiums to be collected and future premiums earned, net of reinsurance at September 30, 2015 : Future premiums (1) Future (1) Three months ended: December 31, 2015 $ 21,054 $ 36,341 Twelve months ended: December 31, 2016 82,229 125,182 December 31, 2017 76,613 105,390 December 31, 2018 71,514 94,004 December 31, 2019 67,678 87,387 Five years ended: December 31, 2024 298,847 359,221 December 31, 2029 248,187 255,225 December 31, 2034 174,358 160,285 December 31, 2039 63,810 65,206 December 31, 2044 23,749 22,408 December 31, 2049 9,518 9,722 December 31, 2054 1,244 2,183 December 31, 2059 5 3 Total $ 1,138,806 $ 1,322,557 (1) Future premiums to be collected is undiscounted which are used to derive the discounted premium receivable asset recorded on Ambac's balance sheet. Future premiums to be earned, net of reinsurance relate to the unearned premium liability and deferred ceded premium asset recorded on Ambac’s balance sheet. The use of contractual lives for many bond types which do not have homogeneous pools of underlying collateral is required in the calculation of the premium receivable, as further described in Note 2. Basis of Presentation and Significant Accounting Principles in the Notes to Consolidated Financial Statements included in Ambac's Annual Report on Form 10-K for the year ended December 31, 2014 . This results in a different premium receivable balance than if expected lives were considered. If installment paying policies are retired or prepay early, premiums reflected in the premium receivable asset and amounts reported in the above table for such policies may not be collected. Future premiums to be earned also considers the use of contractual lives for many bond types which do not have homogeneous pools of underlying collateral, which results in higher unearned premium than if expected lives were considered. If those bonds types are retired early, premium earnings may be negative in the period of call or refinancing. Loss and Loss Expense Reserves: The loss and loss expense reserve (“loss reserve”) policy for financial guarantee insurance relates only to Ambac’s non-derivative insurance business for insurance policies issued to beneficiaries, including VIEs, for which we do not consolidate the VIE. Losses and loss expenses are based upon estimates of the ultimate aggregate losses inherent in the non-derivative financial guarantee portfolio as of the reporting date. A loss reserve is recorded on the balance sheet on a policy-by-policy basis. Loss reserve components of an insurance policy include unpaid claims and the present value ("PV") of expected net cash flows required to be paid under an insurance contract, further described below: • Unpaid claims represent the sum of (i) claims presented and not yet paid for policies allocated to the Segregated Account, including Deferred Amounts and (ii) accrued interest on Deferred Amounts as required by the amended Segregated Account Rehabilitation Plan that became effective on June 12, 2014. Refer to Note 1. Background and Business Description in the Notes to Consolidated Financial Statements included in Ambac's Annual Report on Form 10-K for further discussion of the amended Segregated Account Rehabilitation Plan. Unpaid claims are measured based on the cost of settling the claims, which is principal plus accrued interest. • The PV of expected net cash flows represents the PV of expected cash outflows less the PV of expected cash inflows. The PV of expected net cash flows are impacted by: (i) expected future claims to be paid under an insurance contract, including the impact of potential settlement outcomes upon future installment premiums, (ii) expected recoveries from contractual breaches of RMBS representations and warranties by transaction sponsors, (iii) excess spread within the underlying transaction's cash flow structure, and (iv) other subrogation recoveries. Expected receipts from third parties within the underlying transaction's cash flow structure relating to contractual breaches in non-RMBS securitizations may also reduce expected future claims. Ambac’s approach to resolving disputes involving contractual breaches by transaction sponsors or other third parties has included negotiations and/or pursuing litigation. Ambac does not include potential recoveries from litigation attributed solely to fraudulent inducement claims in our estimate of subrogation recoveries, since any remedies under such claims would be non-contractual. Net cash outflow policies represent contracts where the sum of unpaid claims plus the PV of expected cash outflows are greater than the PV of expected cash inflows. For such policies, a “Loss and loss expense reserves” liability is recorded for the sum of: (i) unpaid claims plus (ii) the excess of the PV of expected net cash outflows over the unearned premium reserve. Net cash inflow policies represent contracts where losses have been paid, but not yet recovered, such that the PV of expected cash inflows are greater than the sum of unpaid claims plus the PV of expected cash outflows. For such policies, a “Subrogation recoverable” asset is recorded for the difference between (i) the PV of expected net cash inflows and (ii) unpaid claims. The approaches used to estimate expected future claims and expected future recoveries considers the likelihood of all possible outcomes. The evaluation process for determining expected losses is subject to certain estimates and judgments based on our assumptions regarding the probability of default by the issuer of the insured security, probability of settlement outcomes (which may include commutation settlements, refinancing and/or other settlement outcomes) and expected severity of credits for each insurance contract. Ambac’s loss reserves are based on management’s on-going review of the financial guarantee credit portfolio. Below are the components of the Loss and loss expense reserves liability and the Subrogation recoverable asset at September 30, 2015 and December 31, 2014 : Unpaid Claims Present Value of Expected Balance Sheet Line Item Claims Accrued Claims and Recoveries Unearned Gross Loss and September 30, 2015: Loss and loss expense reserves $ 2,193,214 $ 324,125 $ 3,137,857 $ (1,238,561 ) $ (179,120 ) $ 4,237,515 Subrogation recoverable 785,993 125,225 148,147 (2,041,567 ) — (982,202 ) Totals $ 2,979,207 $ 449,350 $ 3,286,004 $ (3,280,128 ) $ (179,120 ) $ 3,255,313 December 31, 2014: Loss and loss expense reserves $ 2,172,041 $ 234,802 $ 3,792,133 $ (1,205,621 ) $ (241,348 ) $ 4,752,007 Subrogation recoverable 772,948 94,425 197,751 (2,018,398 ) — (953,274 ) Totals $ 2,944,989 $ 329,227 $ 3,989,884 $ (3,224,019 ) $ (241,348 ) $ 3,798,733 Below is the loss and loss expense reserve roll-forward, net of subrogation recoverable and reinsurance, for the affected periods: Nine Months Ended September 30, 2015 2014 Beginning gross loss and loss expense reserves $ 3,798,733 $ 5,470,234 Less reinsurance on loss and loss expense reserves 100,355 122,357 Beginning balance of net loss and loss expense reserves $ 3,698,378 $ 5,347,877 Changes in the loss and loss expense reserves due to: Current year: Establishment of new loss and loss expense reserves, gross of RMBS subrogation and net of reinsurance 1,404 236 Claim and loss expense (payments) recoveries, net of subrogation and reinsurance — (4 ) Total current year 1,404 232 Prior years: Change in previously established loss and loss expense reserves, gross of RMBS subrogation and net of reinsurance (414,642 ) (934 ) Claim and loss expense (payments) recoveries, net of subrogation and reinsurance (61,740 ) 67,736 (Increase) decrease in previously established RMBS subrogation recoveries, net of reinsurance (31,744 ) (6,315 ) Total prior years (508,126 ) 60,487 Net change in net loss and loss expense reserves (506,722 ) 60,719 Ending net loss and loss expense reserves 3,191,656 5,408,596 Add reinsurance on loss and loss expense reserves (1) 63,657 105,641 Ending gross loss and loss expense reserves $ 3,255,313 $ 5,514,237 (1) Reinsurance recoverable reported on the Balance Sheet also includes reinsurance recoverables (payables) of previously presented loss and loss expenses of $4,662 and $(130) as of September 30, 2015 and 2014 , respectively. The positive development in loss and loss expense reserves established in prior years for the nine months ended September 30, 2015 was primarily due to the impact of commutations in the student loan portfolio and reduced future claims for both the Ambac UK and RMBS portfolios partially offset by negative development in certain public finance transactions and interest accrued on Deferred Amounts. The negative development in loss and loss expense reserves established in prior years for the nine months ended September 30, 2014 was primarily due to the addition of accrued interest on Deferred Amounts pursuant to the amended Segregated Account Rehabilitation Plan offset by improved performance in all sectors, including RMBS, international municipal and other structured finance. The net change in net loss and loss expense reserves are included in losses and loss expenses in the Consolidated Statements of Total Comprehensive Income. Reinsurance recoveries of losses included in losses and loss expenses in the Consolidated Statements of Total Comprehensive Income were an expense of $6,907 and $30,727 for the three and nine months ended September 30, 2015 compared to an expense of $3,885 and $16,045 for the three and nine months ended September 30, 2014 , respectively. The tables below summarize information related to policies currently included in Ambac’s loss and loss expense reserves or subrogation recoverable at September 30, 2015 and December 31, 2014 . Gross par exposures include capital appreciation bonds which are reported at the par amount at the time of issuance of the insurance policy. The weighted average risk-free rate used to discount loss reserves at September 30, 2015 and December 31, 2014 was 2.3% and 2.3% , respectively. Surveillance Categories as of September 30, 2015 I/SL IA II III IV V Total Number of policies 44 17 30 65 164 3 323 Remaining weighted-average contract period (in years) 7 17 14 19 14 6 16 Gross insured contractual payments outstanding: Principal $ 2,099,540 $ 305,681 $ 1,338,428 $ 3,913,273 $ 8,897,699 $ 54,590 $ 16,609,211 Interest 730,755 138,831 356,410 2,940,877 1,827,031 18,157 6,012,061 Total $ 2,830,295 $ 444,512 $ 1,694,838 $ 6,854,150 $ 10,724,730 $ 72,747 $ 22,621,272 Gross undiscounted claim liability (1) $ 15,820 $ 6,036 $ 46,817 $ 1,639,016 $ 6,076,327 $ 72,747 $ 7,856,763 Discount, gross claim liability (786 ) (596 ) (12,179 ) (524,462 ) (697,119 ) (6,146 ) (1,241,288 ) Gross claim liability before all subrogation and before reinsurance $ 15,034 $ 5,440 $ 34,638 $ 1,114,554 $ 5,379,208 $ 66,601 $ 6,615,475 Less: Gross RMBS subrogation (2) — — — — (2,569,094 ) — (2,569,094 ) Discount, RMBS subrogation — — — — 13,633 — 13,633 Discounted RMBS subrogation, before reinsurance — — — — (2,555,461 ) — (2,555,461 ) Less: Gross other subrogation (3) — — (12,719 ) (133,640 ) (641,812 ) (13,219 ) (801,390 ) Discount, other subrogation — — 3,538 35,910 33,468 3,807 76,723 Discounted other subrogation, before reinsurance — — (9,181 ) (97,730 ) (608,344 ) (9,412 ) (724,667 ) Gross claim liability, net of all subrogation and discounts, before reinsurance $ 15,034 $ 5,440 $ 25,457 $ 1,016,824 $ 2,215,403 $ 57,189 $ 3,335,347 Less: Unearned premium revenue (10,207 ) (2,089 ) (17,961 ) (86,842 ) (61,546 ) (475 ) (179,120 ) Plus: Loss expense reserves — 80 819 18,708 79,479 — 99,086 Gross loss and loss expense reserves $ 4,827 $ 3,431 $ 8,315 $ 948,690 $ 2,233,336 $ 56,714 $ 3,255,313 Reinsurance recoverable reported on Balance Sheet (4) $ 641 $ 895 $ 67 $ 82,496 $ (15,780 ) $ — $ 68,319 (1) Gross undiscounted claim liability includes unpaid claims, including accrued interest on Deferred Amounts, on policies allocated to the Segregated Account and Ambac's estimate of expected future claims. (2) RMBS subrogation represents Ambac’s probability-weighted estimate of subrogation recoveries from RMBS transaction sponsors for representation and warranty ("R&W") breaches. (3) Other subrogation primarily represents subrogation related to excess spread or other contractual cash flows on public finance and structured finance transactions, including RMBS. (4) Reinsurance recoverable reported on Balance Sheet includes reinsurance recoverables of $63,657 related to future loss and loss expenses and $4,662 related to presented loss and loss expenses. Surveillance Categories as of December 31, 2014 I/SL IA II III IV V Total Number of policies 36 26 33 69 160 1 325 Remaining weighted-average contract period (in years) 8 12 15 21 12 6 16 Gross insured contractual payments outstanding: Principal $ 1,026,513 $ 519,291 $ 3,091,744 $ 3,792,559 $ 9,892,760 $ 47 $ 18,322,914 Interest 418,746 212,296 1,878,770 2,765,537 1,979,627 19 7,254,995 Total $ 1,445,259 $ 731,587 $ 4,970,514 $ 6,558,096 $ 11,872,387 $ 66 $ 25,577,909 Gross undiscounted claim liability (1) $ 16,360 $ 11,525 $ 155,488 $ 2,040,402 $ 6,456,139 $ 60 $ 8,679,974 Discount, gross claim liability (1,147 ) (937 ) (16,438 ) (716,812 ) (774,611 ) (3 ) (1,509,948 ) Gross claim liability before all subrogation and before reinsurance $ 15,213 $ 10,588 $ 139,050 $ 1,323,590 $ 5,681,528 $ 57 $ 7,170,026 Less: Gross RMBS subrogation (2) — — — — (2,541,219 ) — (2,541,219 ) Discount, RMBS subrogation — — — — 17,679 — 17,679 Discounted RMBS subrogation, before reinsurance — — — — (2,523,540 ) — (2,523,540 ) Less: Gross other subrogation (3) — — (18,034 ) (127,143 ) (647,110 ) — (792,287 ) Discount, other subrogation — — 6,069 36,779 48,960 — 91,808 Discounted other subrogation, before reinsurance — — (11,965 ) (90,364 ) (598,150 ) — (700,479 ) Gross claim liability, net of all subrogation and discounts, before reinsurance $ 15,213 $ 10,588 $ 127,085 $ 1,233,226 $ 2,559,838 $ 57 $ 3,946,007 Less: Unearned premium revenue (10,945 ) (3,432 ) (73,749 ) (88,332 ) (64,890 ) — (241,348 ) Plus: Loss expense reserves 3 1,303 1,968 6,470 84,330 — 94,074 Gross loss and loss expense reserves $ 4,271 $ 8,459 $ 55,304 $ 1,151,364 $ 2,579,278 $ 57 $ 3,798,733 Reinsurance recoverable reported on Balance Sheet (4) $ 73 $ 890 $ 1,355 $ 110,957 $ (13,437 ) $ — $ 99,838 (1) Gross undiscounted claim liability includes unpaid claims, including accrued interest on Deferred Amounts, on policies allocated to the Segregated Account and Ambac's estimate of expected future claims. (2) RMBS subrogation represents Ambac’s probability-weighted estimate of subrogation recoveries from RMBS transaction sponsors for R&W breaches. (3) Other subrogation primarily represents subrogation related to excess spread or other contractual cash flows on public finance and structured finance transactions, including RMBS. (4) Reinsurance recoverable reported on Balance Sheet includes reinsurance recoverables of $100,355 related to future loss and loss expenses and $(517) related to presented loss and loss expenses. Ambac records estimated subrogation recoveries for breaches of representations and warranties (R&W) by sponsors of certain RMBS transactions. Prior to the June 30, 2014 reporting period, Ambac utilized the Adverse and Random Sample approaches to estimate R&W subrogation recoveries for certain RMBS transactions. For a discussion of these subrogation recovery approaches, see Note 2. Basis of Presentation and Significant Accounting Policies in the Notes to Consolidated Financial Statements included Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 . Beginning with the June 30, 2014 reporting period, as a result of gaining further access to loan files, the Random Sample approach has been utilized for all transactions which were previously evaluated using the Adverse Sample approach. From time to time R&W subrogation may include estimates of potential sponsor settlements that are currently in negotiation, but have not been subject to a sampling approach. However, such estimates are not material to Ambac’s financial results and therefore are included in the Random Sample section of this table. Ambac has recorded RMBS subrogation recoveries of $2,555,461 ( $2,528,260 net of reinsurance) and $2,523,540 ( $2,496,515 net of reinsurance) at September 30, 2015 and December 31, 2014 , respectively. The balance of RMBS subrogation recoveries and the related loss reserves, using random samples as the estimation approach, at September 30, 2015 and December 31, 2014 , are as follows: Random Samples Approach Gross loss (1) Subrogation (2)(3) Gross loss At September 30, 2015 $ 1,856,754 $ (2,555,461 ) $ (698,707 ) At December 31, 2014 $ 1,897,426 $ (2,523,540 ) $ (626,114 ) (1) Includes unpaid RMBS claims, including accrued interest on Deferred Amounts, on policies allocated to the Segregated Account. (2) The amount of recorded subrogation recoveries related to each securitization is limited to ever-to-date paid and unpaid losses plus the present value of expected cash flows for each policy. To the extent losses have been paid but not yet fully recovered, the recorded amount of RMBS subrogation recoveries may exceed the sum of the unpaid claims and the present value of expected cash flows for a given policy. The net cash inflow for these policies is recorded as a “Subrogation recoverable” asset. For those transactions where the subrogation recovery is less than the sum of unpaid claims and the present value of expected cash flows, the net cash outflow for these policies is recorded as a “Loss and loss expense reserves” liability. (3) The sponsor’s repurchase obligation may differ depending on the terms of the particular transaction and the status of the specific loan, such as whether it is performing or has been liquidated or charged off. The estimated subrogation recovery for these transactions is based primarily on loan level data provided through trustee reports received in the normal course of our surveillance activities or provided by the sponsor. While this data may not include all the components of the sponsor’s contractual repurchase obligation we believe it is the best information available to estimate the subrogation recovery. Below is the rollforward of RMBS subrogation, by estimation approach, for the affected periods: Random Adverse Total Discounted RMBS subrogation (gross of reinsurance) at January 1, 2015 $ 2,523,540 $ — $ 2,523,540 Changes recognized in 2015: Impact of sponsor actions (2) — — — All other changes (3) 31,921 — 31,921 Discounted RMBS subrogation (gross of reinsurance) at September 30, 2015 $ 2,555,461 $ — $ 2,555,461 Discounted RMBS subrogation (gross of reinsurance) at January 1, 2014 $ 953,825 $ 1,252,773 $ 2,206,598 Changes recognized in 2014: Additional transactions reviewed 24,565 — 24,565 Changes in estimation approach (1) 1,272,532 (1,218,681 ) 53,851 Impact of sponsor actions (2) (90,000 ) — (90,000 ) All other changes (3) 53,508 (34,092 ) 19,416 Discounted RMBS subrogation (gross of reinsurance) at September 30, 2014 $ 2,214,430 $ — $ 2,214,430 (1) Represents estimated subrogation for those transactions previously evaluated using the Adverse sample approach, which are evaluated using a Random Sample approach beginning June 30, 2014. The amounts shown in the Random and Adverse Sample columns are different as a result of the differences in estimation approaches. (2) Sponsor actions include loan repurchases, direct payments to Ambac and other contributions. (3) All other changes which may impact RMBS subrogation recoveries include changes in actual or projected collateral performance, changes in the creditworthiness of a sponsor, and/or the projected timing of recoveries. All other changes may also include estimates of potential sponsor settlements that are currently in negotiation but have not been subject to a sampling approach. However, such estimates are not material to Ambac’s financial results and therefore are included in the Random Sample column of this table. Insurance intangible asset: The insurance intangible amortization expense is included in insurance intangible amortization on the Consolidated Statements of Total Comprehensive Income. For the three and nine months ended September 30, 2015 , the insurance intangible amortization expense was $39,680 and $115,200 , respectively, and for the three and nine months ended September 30, 2014 , the insurance intangible amortization expense was $41,908 and $109,878 , respectively. As of September 30, 2015 and December 31, 2014 , the gross carrying value of the insurance intangible asset was $1,641,852 and $ 1,660,125 , respectively. Accumulated amortization of the insurance intangible asset was $362,404 and $249,205 , as of September 30, 2015 and December 31, 2014 , respectively, resulting in a net insurance intangible asset of $1,279,448 and $1,410,920 , respectively. The estimated future amortization expense for the net insurance intangible asset is as follows: 2015 2016 2017 2018 2019 Thereafter Amortization expense $ 29,892 $ 110,315 $ 97,714 $ 89,267 $ 82,506 $ 869,754

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	7. FAIR VALUE MEASUREMENTS The Fair Value Measurement Topic of the ASC establishes a framework for measuring fair value and disclosures about fair value measurements. Fair Value Hierarchy: The Fair Value Measurement Topic of the ASC specifies a fair value hierarchy based on whether the inputs to valuation techniques used to measure fair value are observable or unobservable. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect Company-based assumptions. The fair value hierarchy prioritizes model inputs into three broad levels as follows: Ÿ Level 1 Quoted prices for identical instruments in active markets. Assets and liabilities classified as Level 1 include US Treasury securities, exchange traded futures contracts, variable rate demand obligations and money market funds. Ÿ Level 2 Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets. Assets and liabilities classified as Level 2 generally include investments in fixed income securities representing municipal, asset-backed and corporate obligations, most financial services derivatives and most long-term debt of variable interest entities consolidated under the Consolidation Topic of the ASC. Also included are equity interests in pooled investment funds measured at fair value where the investment can be redeemed in the near term at a value based on the net asset value. Ÿ Level 3 Model derived valuations in which one or more significant inputs or significant value drivers are unobservable. This hierarchy requires the use of observable market data when available. Assets and liabilities classified as Level 3 include credit derivative contracts written as part of the financial guarantee business, certain financial services interest rate swap contracts, equity interests in Ambac sponsored special purpose entities and certain investments in fixed income securities. Additionally, Level 3 assets and liabilities generally include fixed income securities, loan receivables, and certain long-term debt of variable interest entities consolidated under the Consolidation Topic of the ASC. The following table sets forth the carrying amount and fair value of Ambac’s financial assets and liabilities as of September 30, 2015 and December 31, 2014 , including the level within the fair value hierarchy at which fair value measurements are categorized. As required by the Fair Value Measurement Topic of the ASC financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Carrying Total Fair Fair Value Measurements Categorized as: Level 1 Level 2 Level 3 September 30, 2015: Financial assets: Fixed income securities: Municipal obligations $ 419,001 $ 419,001 $ — $ 419,001 $ — Corporate obligations 1,587,578 1,587,578 — 1,587,578 — Foreign obligations 103,654 103,654 — 103,654 — U.S. government obligations 30,863 30,863 30,863 — — U.S. agency obligations 4,281 4,281 — 4,281 — Residential mortgage-backed securities 1,871,483 1,871,483 — 1,487,694 383,789 Collateralized debt obligations 81,912 81,912 — 81,912 — Other asset-backed securities 858,104 858,104 — 858,104 — Fixed income securities, pledged as collateral: U.S. government obligations 64,972 64,972 64,972 — — Short term investments 364,780 364,780 305,950 58,830 — Other investments 314,934 302,791 — 290,723 12,068 Cash and cash equivalents 27,099 27,099 27,099 — — Loans 5,499 5,479 — — 5,479 Derivative assets: Credit derivatives 1,345 1,345 — — 1,345 Interest rate swaps—asset position 89,743 89,743 — 23,796 65,947 Interest rate swaps—liability position — — — — — Futures contracts — — — — — Other assets 9,322 9,322 — — 9,322 Variable interest entity assets: Fixed income securities: Corporate obligations 2,679,895 2,679,895 — — 2,679,895 Restricted cash 5,895 5,895 5,895 — — Loans 12,183,061 12,183,061 — — 12,183,061 Total financial assets $ 20,703,421 $ 20,691,258 $ 434,779 $ 4,915,573 $ 15,340,906 Financial liabilities: Obligations under investment agreements $ 100,358 $ 100,858 $ — $ — $ 100,858 Long term debt, including accrued interest 1,457,996 1,318,300 — 139,002 1,179,298 Derivative liabilities: Credit derivatives 31,232 31,232 — — 31,232 Interest rate swaps—asset position (63,785 ) (63,785 ) — (63,785 ) — Interest rate swaps—liability position 408,168 408,168 — 270,049 138,119 Futures contracts 220 220 220 — — Liabilities for net financial guarantees written (1) 2,414,692 3,044,698 — — 3,044,698 Variable interest entity liabilities: Long-term debt 12,791,012 12,791,012 — 10,647,480 2,143,532 Derivative liabilities: Interest rate swaps—liability position 2,065,224 2,065,224 — 2,065,224 — Currency swaps—asset position (31,429 ) (31,429 ) — (31,429 ) — Total financial liabilities $ 19,173,688 $ 19,664,498 $ 220 $ 13,026,541 $ 6,637,737 (1) The carrying value of net financial guarantees written includes the following balance sheet items: Premium receivables; Reinsurance recoverable on paid and unpaid losses; Deferred ceded premium; Subrogation recoverable; Insurance intangible asset; Unearned premiums; Loss and loss expense reserves; Ceded premiums payable, premiums taxes payable and other deferred fees recorded in Other liabilities. Carrying Total Fair Fair Value Measurements Categorized as: Level 1 Level 2 Level 3 December 31, 2014: Financial assets: Fixed income securities: Municipal obligations $ 525,792 $ 525,792 $ — $ 525,792 $ — Corporate obligations 1,385,594 1,385,594 — 1,381,786 3,808 Foreign obligations 127,757 127,757 — 127,757 — U.S. government obligations 42,979 42,979 42,979 — — U.S. agency obligations 29,486 29,486 — 29,486 — Residential mortgage-backed securities 1,710,955 1,710,955 — 1,516,562 194,393 Collateralized debt obligations 21,122 21,122 — 21,122 — Other asset-backed securities 882,001 882,001 — 882,001 — Fixed income securities, pledged as collateral: U.S. government obligations 64,267 64,267 64,267 — — Short term investments 360,065 360,065 358,190 1,875 — Other investments 357,016 349,468 — 336,013 13,455 Cash and cash equivalents 73,903 73,903 73,903 — — Loans 5,714 5,634 — — 5,634 Derivative assets: Credit derivatives 2,043 2,043 — — 2,043 Interest rate swaps—asset position 106,974 106,974 — 106,974 — Interest rate swaps—liability position — — — — — Futures contracts — — — — — Other assets 12,036 12,036 — — 12,036 Variable interest entity assets: Fixed income securities: Corporate obligations 2,743,050 2,743,050 — — 2,743,050 Restricted cash 7,708 7,708 7,708 — — Loans 12,371,177 12,371,177 — — 12,371,177 Total financial assets $ 20,829,639 $ 20,822,011 $ 547,047 $ 4,929,368 $ 15,345,596 Financial liabilities: Obligations under investment agreements $ 160,079 $ 161,821 $ — $ — $ 161,821 Long term debt, including accrued interest 1,273,805 1,379,864 — — 1,379,864 Derivative liabilities: Credit derivatives 75,502 75,502 — — 75,502 Interest rate swaps—asset position (54,666 ) (54,666 ) — (54,666 ) — Interest rate swaps—liability position 385,546 385,546 — 243,659 141,887 Futures contracts 562 562 562 — — Other contracts — — — — — Liabilities for net financial guarantees written (1) 2,923,652 4,539,000 — — 4,539,000 Variable interest entity liabilities: Long-term debt 12,882,076 12,882,076 — 11,618,412 1,263,664 Derivative liabilities: Interest rate swaps—liability position 2,133,268 2,133,268 — 2,133,268 — Currency swaps—liability position 66,895 66,895 — 66,895 — Total financial liabilities $ 19,846,719 $ 21,569,868 $ 562 $ 14,007,568 $ 7,561,738 (1) The carrying value of net financial guarantees written includes the following balance sheet items: Premium receivables; Reinsurance recoverable on paid and unpaid losses; Deferred ceded premium; Subrogation recoverable; Insurance intangible asset; Unearned premiums; Loss and loss expense reserves; Ceded premiums payable, premiums taxes payable and other deferred fees recorded in Other liabilities. Determination of Fair Value: When available, Ambac uses quoted active market prices specific to the financial instrument to determine fair value, and classifies such items within Level 1. Because many fixed income securities do not trade on a daily basis, pricing sources apply available information through processes such as matrix pricing to calculate fair value. In those cases, the items are classified within Level 2. If quoted market prices are not available, fair value is based upon models that use, where possible, current market-based or independently-sourced market parameters. Items valued using valuation models are classified according to the lowest level input or value driver that is significant to the valuation. Thus, an item may be classified in Level 3 even though there may be significant inputs that are readily observable. The determination of fair value for financial instruments categorized in Level 2 or 3 involves significant judgment due to the complexity of factors contributing to the valuation. Third-party sources from which we obtain independent market quotes also use assumptions, judgments and estimates in determining financial instrument values and different third parties may use different methodologies or provide different prices for securities. In addition, the use of internal valuation models may require assumptions about hypothetical or inactive markets. As a result of these factors, the actual trade value of a financial instrument in the market, or exit value of a financial instrument position by Ambac, may be significantly different from its recorded fair value. Ambac’s financial instruments carried at fair value are mainly comprised of investments in fixed income securities, equity interests in pooled investment funds, derivative instruments, variable interest entity assets and liabilities and equity interests in Ambac sponsored special purpose entities. Valuation of financial instruments is performed by Ambac’s finance group using methods approved by senior financial management with consultation from risk management and portfolio managers as appropriate. Preliminary valuation results are discussed with portfolio managers quarterly to assess consistency with market transactions and trends as applicable. Market transactions such as trades or negotiated settlements of similar positions, if any, are reviewed quarterly to validate fair value model results. However many of the financial instruments valued using significant unobservable inputs have very little or no observable market activity. Methods and significant inputs and assumptions used to determine fair values across portfolios are reviewed quarterly by senior financial management. Other valuation control procedures specific to particular portfolios are described further below. We reflect Ambac’s own creditworthiness in the fair value of financial liabilities by including a credit valuation adjustment (“CVA”) in the determination of fair value. A decline (increase) in Ambac’s creditworthiness as perceived by market participants will generally result in a higher (lower) CVA, thereby lowering (increasing) the fair value of Ambac’s financial liabilities as reported. Fixed Income Securities: The fair values of fixed income investment securities are based primarily on market prices received from dealer quotes or alternative pricing sources with reasonable levels of price transparency. Such quotes generally consider a variety of factors, including recent trades of the same and similar securities. For those fixed income investments where quotes were not available or cannot be reasonably corroborated, fair values are based on internal valuation models. Key inputs to the internal valuation models generally include maturity date, coupon and yield curves for asset-type and credit rating characteristics that closely match those characteristics of the specific investment securities being valued. Longer (shorter) expected maturities or higher (lower) yields used in the valuation model will, in isolation, result in decreases (increases) in fair value. Generally, lower credit ratings or longer expected maturities will be accompanied by higher yields used to value a security. Certain investments in Ambac insured securities for which projected cash flows consist solely of Deferred Amounts and interest thereon, are internally valued based upon the valuation of surplus notes. At September 30, 2015 , approximately 9% , 84% , and 7% of the investment portfolio (excluding variable interest entity investments) was valued using dealer quotes, alternative pricing sources with reasonable levels of price transparency and internal valuation models, respectively. At December 31, 2014 , approximately 10% , 86% , and 4% of the investment portfolio (excluding variable interest entity investments) was valued using dealer quotes, alternative pricing sources with reasonable levels of price transparency and internal valuation models, respectively. Ambac performs various review and validation procedures to quoted and modeled prices for fixed income securities, including price variance analysis, missing and static price reviews, overall valuation analysis by senior traders and finance managers and reviews associated with our ongoing impairment analysis. Unusual prices identified through these procedures will be evaluated further against alternative third party quotes (if available) and/or internally modeled prices, and the pricing source values will be challenged as necessary. Price challenges generally result in the use of the pricing source’s quote as originally provided or as revised by the source following their internal diligence process. A price challenge may result in a determination by either the pricing source or Ambac management that the pricing source cannot provide a reasonable value for a security or cannot adequately support a quote, in which case Ambac would resort to using either other quotes or internal models. Results of price challenges are reviewed by senior traders and finance managers. Information about the valuation inputs for fixed income securities classified as Level 3 is included below: Corporate obligations: These securities represent interest only strips of investment grade corporate obligations. The fair value of such securities classified as Level 3 was $0 and $3,808 at September 30, 2015 and December 31, 2014 , respectively. Fair value was calculated using a discounted cash flow approach with the discount rate determined from the yields of corporate bonds from the same issuers. Significant inputs for the interest only strips valuation at December 31, 2014 include the following weighted averages: a. Coupon rate: 0.345% b. Maturity: 19.14 years c. Yield: 4.93% Residential mortgage-backed securities: These securities are guaranteed under policies that are subject to the Segregated Account Rehabilitation Plan and have projected future cash flows consisting solely of Deferred Amounts under such policies including interest thereon. The fair value of such securities classified as Level 3 was $383,789 and $194,393 at September 30, 2015 and December 31, 2014 , respectively. Fair value was calculated based on the valuation of Ambac Assurance surplus notes which, under the terms of the Segregated Account Rehabilitation Plan, are to be redeemed in proportion with the payment of Deferred Amounts on or about the dates when such payments are made. Refer to Note 1. Background and Business Description and to Note 1. Background and Business Description in the Notes to Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 for further description of the Segregated Account Rehabilitation Plan and its impact on the payment of Segregated Account policy claims and surplus note redemptions. Other Investments: Other investments primarily relate to investments in pooled investment funds, which are valued using the net asset value (“NAV”) per share, calculated on at least a monthly basis where NAV is the basis for determining the redemption value of the investment. These investments are classified as Level 2 as redemptions may be made in the near term (within 90 days) without significant impediments or restrictions. Ambac assesses impediments to redemption and other factors that may restrict the ability to redeem investments in the near term or at values approximating the NAV and may classify the investments as Level 3 if such factors exist. Other investments also includes Ambac's interest in a non-consolidated VIE, which is carried under the equity method. Valuation of this equity interest is internally calculated using a discounted cash flow approach and is classified as Level 3. Derivative Instruments: Ambac’s derivative instruments primarily comprise interest rate and credit default swaps and exchange traded futures contracts. Fair value is determined based upon market quotes from independent sources, when available. When independent quotes are not available, fair value is determined using valuation models. These valuation models require market-driven inputs, including contractual terms, credit spreads and ratings on underlying referenced obligations, yield curves and tax-exempt interest ratios. The valuation of certain interest rate as well as all credit derivative contracts also require the use of data inputs and assumptions that are determined by management and are not readily observable in the market. Under the Fair Value Measurement Topic of the ASC, Ambac is required to consider its own credit risk when measuring the fair value of derivatives and other liabilities. The fair value of credit derivative liabilities was reduced by $8,497 and $15,910 at September 30, 2015 and December 31, 2014 , respectively, as a result of incorporating a CVA into the valuation model for these transactions. Interest rate swaps and other derivative liabilities may also require an adjustment to fair value to reflect Ambac’s credit risk. Derivative liabilities were reduced by $83,983 and $64,547 at September 30, 2015 and December 31, 2014 , as a result of Ambac CVA adjustments to derivative contracts other than credit derivatives. Additional factors considered in estimating the amount of any Ambac CVA on such contracts include collateral posting provisions, right of set-off with the counterparty, the period of time remaining on the derivatives and the pricing of recent terminations. As described further below, certain valuation models require other inputs that are not readily observable in the market. The selection of a model to value a derivative depends on the contractual terms of, and specific risks inherent in the instrument as well as the availability of pricing information in the market. For derivatives that are less complex and trade in liquid markets or may be valued primarily by reference to interest rates and yield curves that are observable and regularly quoted, such as interest rate swaps, we utilize vendor-developed models. These models provide the net present value of the derivatives based on contractual terms and observable market data. Downgrades of Ambac Assurance, as guarantor of the financial services derivatives, have increased collateral requirements and triggered termination provisions in certain interest rate swaps. Termination activity since the initial rating downgrades of Ambac Assurance provided additional information about the replacement and/or exit value of certain financial services derivatives, which has been incorporated into the fair value of these derivatives as appropriate. Generally, the need for counterparty (or Ambac) CVAs is mitigated by the existence of collateral posting agreements under which adequate collateral has been posted. Derivative contracts entered into with financial guarantee customers are not subject to collateral posting agreements. Counterparty credit risk related to such customer derivative assets is included in our fair value adjustments. For derivatives that do not trade, or trade in less liquid markets such as credit derivatives, an internal model is used because such instruments tend to be unique, contain complex or heavily modified and negotiated terms, and pricing information is not readily available in the market. Derivative fair value models and the related assumptions are continuously re-evaluated by management and enhanced, as appropriate, based on improvements in modeling techniques. Ambac has not made any significant changes to its modeling techniques or related model inputs for the periods presented. Credit Derivatives (“CDS”): Fair value of Ambac’s CDS is determined using internal valuation models and represents the net present value of the difference between the fees Ambac originally charged for the credit protection and our estimate of what a financial guarantor of comparable credit quality would hypothetically charge to provide the same protection at the balance sheet date. Ambac competed in the financial guarantee market, which differs from the credit markets where Ambac-insured obligations may trade. As a financial guarantor, Ambac assumes only credit risk; we do not assume other risks and costs inherent in direct ownership of the underlying reference securities. Additionally, as a result of having the ability to influence our CDS counterparty in certain investor decisions, financial guarantors generally have the ability to actively remediate the credit, potentially reducing the loss given a default. Financial guarantee contracts, including CDS, issued by Ambac and its competitors are typically priced to capture some portion of the spread that would be observed in the capital markets for the underlying (insured) obligation. Such pricing was well established by historical financial guarantee fees relative to capital market spreads as observed and executed in competitive markets, including in financial guarantee reinsurance and secondary market transactions. Because of this relationship and in the absence of severe credit deterioration, changes in the fair value of our credit default swaps will generally be less than changes in the fair value of the underlying reference obligations. Key variables used in our valuation of substantially all of our credit derivatives include the balance of unpaid notional, expected term, fair values of the underlying reference obligations, reference obligation credit ratings, assumptions about current financial guarantee CDS fee levels relative to reference obligation spreads and the CVA applied against Ambac Assurance liabilities by market participants. Notional balances, expected remaining term and reference obligation credit ratings are monitored and determined by Ambac’s portfolio risk management group. Fair values of the underlying reference obligations are obtained from broker quotes when available, or are estimated internally. Implicit in the fair values we obtain on the underlying reference obligations are the market’s assumptions about default probabilities, default timing, correlation, recovery rates and collateral values. Broker quotes on the reference obligations named in our CDS contracts represent an input to determine the estimated fair value of the CDS contract. Broker quotes are indicative values for the reference obligation and generally do not represent a bid for the reference instrument. Such quotes follow methodologies that are generally consistent with those used to value similar assets on the quote providers’ own books. Methodologies may differ among brokers but are understood to reflect observable trading activity (when available) and modeling that relies on empirical data and reasonable assumptions. For certain CDS contracts referencing unsecuritized pools of assets, we will obtain counterparty quotes on the credit derivative itself. Such quotes are adjusted to reflect Ambac’s own credit risk when determining the fair value of credit derivative liabilities. Third party reference obligation values or specific credit derivative quotes were used in the determination of CDS fair values related to transactions representing 85% of CDS gross par outstanding and 49% of the CDS derivative liability as of September 30, 2015 . When broker quotes for reference obligations are not available, reference obligation prices used in the valuation model are estimated internally based on available market prices or spreads for securities or indices with similar characteristics such as underlying collateral, credit rating and expected life. Internal estimates may also consider historical quotes on the reference obligation, updated for changes in market factors and security specific developments such as credit rating changes. Reference obligation prices derived internally as described above were used in the determination of CDS fair values related to transactions representing 15% of CDS gross par outstanding and 51% of the CDS derivative liability as of September 30, 2015 . Ambac’s CDS fair value calculations are adjusted for changes in our estimates of expected loss on the reference obligations and observable changes in financial guarantee market pricing. If no adjustment is considered necessary, Ambac maintains the same percentage of the credit spread (over LIBOR) demanded in the market for the reference obligation as existed at the inception of the CDS. Therefore, absent changes in expected loss on the reference obligations or financial guarantee CDS market pricing, the financial guarantee CDS fee used for a particular contract in Ambac’s fair value calculations represent a consistent percentage, period to period, of the credit spread determinable from the reference obligation value at the balance sheet date. This results in a CDS fair value balance that fluctuates in proportion with the reference obligation value. The amount of expected loss on a reference obligation is a function of the probability that the obligation will default and severity of loss in the event of default. Ambac’s CDS transactions were all originally underwritten with extremely low expected losses. Both the reference obligation spreads and Ambac’s CDS fees at the inception of these transactions reflected these low expected losses. When reference obligations experience credit deterioration, there is an increase in the probability of default on the obligation and, therefore, an increase in expected loss. Ambac reflects the effects of changes in expected loss on the fair value of its CDS contracts by increasing the percentage of the reference obligation spread (over LIBOR) which would be captured as a CDS fee (“relative change ratio”) at the valuation date, resulting in a higher mark-to-market loss on our CDS relative to any price decline on the reference obligation. The fundamental assumption is that financial guarantee CDS fees will increase relative to reference obligation spreads as the underlying credit quality of the reference obligation deteriorates and approaches payment default. For example, if the credit spread of an underlying reference obligation was 80 basis points at the inception of a transaction and Ambac received a 20 basis point fee for issuing a CDS on that obligation, the relative change ratio, which represents the CDS fee to cash market spread Ambac would utilize in its valuation calculation, would be 25% . If the reference obligation spread increased to 100 basis points in the current reporting period, absent any observable changes in financial guarantee CDS market pricing or credit deterioration, Ambac’s current period CDS fee would be computed by multiplying the current reference obligation spread of 100 basis points by the relative change ratio of 25% , resulting in a 25 basis point fee. Thus, the model indicates we would need to receive an additional 5 basis points (25 basis points currently less the 20 basis points contractually received) for issuing a CDS in the current reporting period for this reference obligation. We would then discount the product of the notional amount of the CDS and the 5 basis point hypothetical CDS fee increase, over the weighted average life of the reference obligation to compute the current period mark-to-market loss. Using the same example, if the reference obligation spread increased to 100 basis points and there was credit deterioration as evidenced by an internal rating downgrade which increased the relative change ratio from 25% to 35% , we would estimate a 15 basis point CDS fee increase in our model ( 35% of 100 basis points reference obligation spread, or 35 basis points currently, less the 20 basis points contractually received). Therefore, we would record a higher mark-to-market loss based on the computations described above absent any observable changes in financial guarantee CDS market pricing. We do not adjust the relative change ratio until an actual internal rating downgrade has occurred unless we observe new pricing on financial guarantee CDS contracts. However, because we have active surveillance procedures in place for our entire CDS portfolio, particularly for transactions at or near a below investment grade threshold, we believe it is unlikely that an internal downgrade would lag the actual credit deterioration of a transaction for any meaningful time period. The factors used to increase the relative change ratio are based on rating agency probability of default percentages determined by management to be appropriate for the relevant bond type. That is, the probability of default associated with the respective tenor and internal rating of each CDS transaction is utilized in the computation of the relative change ratio in our CDS valuation model. The new relative change ratio in the event of an internal downgrade of the reference obligation is calculated as the weighted average of: (i) a given transaction’s inception relative change ratio and (ii) a ratio of 100%. The weight given to the inception relative change ratio is 100% minus the current probability of default (the probability of non-default) and the weight given to using a 100% relative change ratio is the probability of default. For example, assume a transaction having an inception relative change ratio of 33% is downgraded to B-during the period, at which time it has an estimated remaining life of 8 years. If the estimated probability of default for an 8 year, B-rated credit of this type is 60% then the revised relative change ratio will be 73.2% . The revised relative change ratio can be calculated as 33% x (100% - 60%) + 100% x 60% = 73.2%. As noted above, reference obligation spreads incorporate market perceptions of default probability and loss severity, as well as liquidity risk and other factors. By increasing the relative change ratio in our calculations proportionally to default probabilities, Ambac incorporates into its CDS fair value the higher expected loss on the reference obligation (probability of default x loss severity), by increasing the portion of reference obligation spread that should be paid to the CDS provider. Ambac incorporates its own credit risk into the valuation of its CDS liabilities by applying a CVA to the calculations described above. Under our methodology, determination of the CDS fair value requires estimating hypothetical financial guarantee CDS fees for a given credit at the valuation date and estimating the present value of those fees. Our approach begins with pricing in the risk of default of the reference obligation using that obligation’s credit spread. The widening of the reference obligation spread results in a mark-to-market loss to Ambac, as the credit protection seller, and a gain to the credit protection buyer because the current cost of credit protection on the reference obligation (ignoring CDS counterparty credit risk) will be greater than the amount of the actual contractual CDS fees. The Ambac CVA represents the difference between the present value of the hypothetical fees discounted at LIBOR compared to rates that incorporate Ambac credit risk. The discount rates used to determine the Ambac CVA are estimated using relevant data points, including quoted prices of securities guaranteed by Ambac Assurance which indicate the value placed by market participants on Ambac Assurance’s insurance obligations and the fair value of Ambac Assurance surplus notes. The resulting Ambac CVA, as a percentage of the CDS mark-to-market liability determined by discounting at LIBOR, was 21.4% and 17.8% as of September 30, 2015 and December 31, 2014 , respectively. In instances where narrower referen

Investments

Investments	9 Months Ended
	Sep. 30, 2015
Investments, Debt and Equity Securities [Abstract]
Investments	8. INVESTMENTS Ambac’s invested assets are primarily comprised of fixed income securities classified as available-for-sale and equity interests in pooled investment funds. Such equity interests in the form of common stock or in-substance common stock are classified as trading securities and are reported within Other investments on the Consolidated Balance Sheets. Other investments also includes Ambac's equity interest in an unconsolidated trust created in connection with its sale of Segregated Account junior surplus notes on August 28, 2014. The amortized cost and estimated fair value of available-for-sale investments, excluding VIE investments, at September 30, 2015 and December 31, 2014 were as follows: Amortized Gross Gross Estimated Non-credit other- (1) September 30, 2015 Fixed income securities: Municipal obligations $ 420,465 $ 5,217 $ 6,681 $ 419,001 $ — Corporate obligations 1,593,457 11,739 17,618 1,587,578 — Foreign obligations 104,226 1,710 2,282 103,654 — U.S. government obligations 30,410 672 219 30,863 — U.S. agency obligations 4,283 — 2 4,281 — Residential mortgage-backed securities 1,797,616 116,052 42,185 1,871,483 27,439 Collateralized debt obligations 82,734 54 876 81,912 — Other asset-backed securities 836,309 23,109 1,314 858,104 — 4,869,500 158,553 71,177 4,956,876 27,439 Short-term 364,784 — 4 364,780 — 5,234,284 158,553 71,181 5,321,656 27,439 Fixed income securities pledged as collateral: U.S. government obligations 64,556 416 — 64,972 — Total collateralized investments 64,556 416 — 64,972 — Total available-for-sale investments $ 5,298,840 $ 158,969 $ 71,181 $ 5,386,628 $ 27,439 December 31, 2014 Fixed income securities: Municipal obligations $ 523,019 $ 9,769 $ 6,996 $ 525,792 $ — Corporate obligations 1,382,195 12,815 9,416 1,385,594 — Foreign obligations 126,041 3,060 1,344 127,757 — U.S. government obligations 42,328 1,078 427 42,979 — U.S. agency obligations 29,524 — 38 29,486 — Residential mortgage-backed securities 1,557,059 167,396 13,500 1,710,955 7,773 Collateralized debt obligations 21,346 50 274 21,122 — Other asset-backed securities 833,366 48,794 159 882,001 — 4,514,878 242,962 32,154 4,725,686 7,773 Short-term 360,069 — 4 360,065 — 4,874,947 242,962 32,158 5,085,751 7,773 Fixed income securities pledged as collateral: U.S. government obligations 64,378 — 111 64,267 — Total collateralized investments 64,378 — 111 64,267 — Total available-for-sale investments $ 4,939,325 $ 242,962 $ 32,269 $ 5,150,018 $ 7,773 (1) Represents the amount of non-credit other-than-temporary impairment losses remaining in accumulated other comprehensive loss on securities that also had a credit impairment. These losses are included in gross unrealized losses as of September 30, 2015 and December 31, 2014 . The amortized cost and estimated fair value of available-for-sale investments, excluding VIE investments, at September 30, 2015 , by contractual maturity, were as follows: Amortized Estimated Due in one year or less $ 534,324 $ 534,445 Due after one year through five years 900,319 899,172 Due after five years through ten years 967,158 961,706 Due after ten years 180,380 179,806 2,582,181 2,575,129 Residential mortgage-backed securities 1,797,616 1,871,483 Collateralized debt obligations 82,734 81,912 Other asset-backed securities 836,309 858,104 Total $ 5,298,840 $ 5,386,628 Expected maturities will differ from contractual maturities because borrowers may have the right to call or prepay certain obligations with or without call or prepayment penalties. Unrealized Losses: The following table shows gross unrealized losses and fair values of Ambac’s available-for-sale investments, aggregated by investment category and length of time that the individual securities have been in a continuous unrealized loss position, at September 30, 2015 and December 31, 2014 : Less Than 12 Months 12 Months or More Total Fair Value Gross Fair Value Gross Fair Value Gross September 30, 2015 Fixed income securities: Municipal obligations $ 91,214 $ 1,751 $ 124,358 $ 4,930 $ 215,572 $ 6,681 Corporate obligations 677,529 15,731 104,242 1,887 781,771 17,618 Foreign obligations 33,646 1,389 7,842 893 41,488 2,282 U.S. government obligations 4,671 150 10,789 69 15,460 219 U.S. agency obligations — — 4,281 2 4,281 2 Residential mortgage-backed securities 626,063 37,165 73,204 5,020 699,267 42,185 Collateralized debt obligations 73,563 876 — — 73,563 876 Other asset-backed securities 428,610 1,285 16,494 29 445,104 1,314 1,935,296 58,347 341,210 12,830 2,276,506 71,177 Short-term 18,822 4 — — 18,822 4 1,954,118 58,351 341,210 12,830 2,295,328 71,181 Fixed income securities, pledged as collateral: U. S. government obligations — — — — — — Total collateralized investments — — — — — — Total temporarily impaired securities $ 1,954,118 $ 58,351 $ 341,210 $ 12,830 $ 2,295,328 $ 71,181 Less Than 12 Months 12 Months or More Total Fair Value Gross Fair Value Gross Fair Value Gross December 31, 2014: Fixed income securities: Municipal obligations $ 77,788 $ 1,244 $ 135,076 $ 5,752 $ 212,864 $ 6,996 Corporate obligations 453,504 4,998 172,045 4,418 625,549 9,416 Foreign obligations 20,827 748 14,277 596 35,104 1,344 U.S. government obligations 7,223 154 14,735 273 21,958 427 U.S. agency obligations 25,039 2 4,378 36 29,417 38 Residential mortgage-backed securities 413,203 12,391 10,076 1,109 423,279 13,500 Collateralized debt obligations 5,012 274 — — 5,012 274 Other asset-backed securities 248,823 155 68 4 248,891 159 1,251,419 19,966 350,655 12,188 1,602,074 32,154 Short-term 8,803 4 — — 8,803 4 1,260,222 19,970 350,655 12,188 1,610,877 32,158 Fixed income securities, pledged as collateral: U. S. government obligations 64,267 111 — — 64,267 111 Total collateralized investments 64,267 111 — — 64,267 111 Total temporarily impaired securities $ 1,324,489 $ 20,081 $ 350,655 $ 12,188 $ 1,675,144 $ 32,269 Management has determined that the unrealized losses reflected in the tables above are temporary in nature as of September 30, 2015 and December 31, 2014 based upon (i) no unexpected principal and interest payment defaults on these securities; (ii) analysis of the creditworthiness of the issuer and financial guarantor, as applicable, and analysis of projected defaults on the underlying collateral; (iii) management has no intent to sell these investments in debt securities; and (iv) it is not more likely than not that Ambac will be required to sell these debt securities before the anticipated recovery of its amortized cost basis. The assessment under (iv) is based on a comparison of future available liquidity from the investment portfolio against the projected net cash outflow from operating activities and debt service. For purposes of this assessment, available liquidity from the investment portfolio is comprised of the fair value of securities for which management has asserted its intent to sell, the fair value of other securities that are available for sale and in an unrealized gain position, trading securities plus the scheduled maturities and interest payments from the remaining securities in the portfolio. To the extent that securities that management intends to sell are in an unrealized loss position, they would have already been considered other-than-temporarily impaired with the amortized cost written down to fair value. Because the above-described assessment indicates that future available liquidity exceeds projected net cash outflow, it is not more likely than not that we would be required to sell securities in an unrealized loss position before the recovery of their amortized cost basis. In the liquidity assessment described above, principal payments on securities pledged as collateral are not considered to be available for other liquidity needs until the collateralized positions are projected to be settled. Projected interest receipts on securities pledged as collateral generally belong to Ambac and are considered to be sources of available liquidity from the investment portfolio. As of September 30, 2015 , for securities that have indications of possible other-than-temporary impairment but which management does not intend to sell and will not more likely than not be required to sell, management compared the present value of cash flows expected to be collected to the amortized cost basis of the securities to assess whether the amortized cost will be recovered. Cash flows were discounted at the effective interest rate implicit in the security at the date of acquisition (or Fresh Start Reporting Date of April 30, 2013 for securities purchased prior to that date) or for debt securities that are beneficial interests in securitized financial assets, at a rate equal to the current yield used to accrete the beneficial interest. For floating rate securities, future cash flows and the discount rate used were both adjusted to reflect changes in the index rate applicable to each security as of the evaluation date. Of the securities that were in a gross unrealized loss position at September 30, 2015 , $788,174 of the total fair value and $44,497 of the unrealized loss related to below investment grade securities and non-rated securities. Of the securities that were in a gross unrealized loss position at December 31, 2014 , $473,656 of the total fair value and $16,001 of the unrealized loss related to below investment grade securities and non-rated securities. With respect to Ambac insured securities guaranteed under policies that have been allocated to the Segregated Account, future cash flows used to measure credit impairment represents the sum of (i) the bond’s intrinsic cash flows and (ii) the estimated Ambac Assurance claim payments, including interest on Deferred Amounts. Ambac estimates the timing of such claim payment receipts but the actual timing of such amounts are at the sole discretion of the Rehabilitator. Further modifications to the Segregated Account Rehabilitation Plan or to the rules and guidelines promulgated thereunder, orders from the Rehabilitation Court or actions by the Rehabilitator with respect to the form, amount and timing of satisfying permitted policy claims, or making payments on Deferred Amounts or surplus notes, may have a material effect on the fair value of Ambac insured securities and future recognition of other-than-temporary impairments. Refer to Note 1. Background and Business Description and to Note 1. Background and Business Description in the Notes to Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 for information relating to the amended Segregated Account Rehabilitation Plan. Ambac’s assessment about whether a decline in value is other-than-temporary reflects management’s current judgment regarding facts and circumstances specific to a security and the factors noted above, including Ambac's intention to sell securities and ability to hold temporarily impaired securities until recovery. If that judgment changes, Ambac may ultimately record a charge for other-than-temporary impairment in future periods. Municipal and corporate obligations The gross unrealized losses on municipal and corporate obligations as of September 30, 2015 are primarily the result of the increase in interest rates since the Fresh Start Reporting Date of April 30, 2013 . These securities are primarily fixed-rate securities with an investment grade credit rating. Management believes that the timely receipt of all principal and interest on these positions is probable . Residential mortgage-backed securities Of the $42,185 of unrealized losses on residential mortgage-backed securities, $40,877 is attributable to Ambac insured securities. The unrealized loss on these securities is primarily the result of discount accretion, which has exceeded the increase in fair value since the Fresh Start Reporting Date of April 30, 2013 . Additionally, the fair value of such securities declined beginning the second quarter of 2015 reflecting the market's view of Ambac's credit risk. As part of the quarterly impairment review process, management estimates expected future cash flows from residential mortgage-backed securities. This approach includes the utilization of market accepted software models in conjunction with detailed data of the historical performance of the collateral pools, which assists in the determination of assumptions such as defaults, severity and voluntary prepayment rates that are largely driven by home price forecasts as well as other macro-economic factors. Additionally, for Ambac insured securities that are allocated to the Segregated Account, expected future cash flows include assumptions about the timing of Ambac Assurance claim payments, including interest on Deferred Amounts, although the actual timing of such payments are at the sole discretion of the Rehabilitator. These assumptions are used to project future cash flows for each security. Management considered this analysis in making our determination that a credit loss has not occurred at September 30, 2015 on these transactions. Realized Gains and Losses and Other-Than-Temporary Impairments: The following table details amounts included in net realized gains and other-than-temporary impairments included in earnings for the affected periods: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Gross realized gains on securities $ 343 $ 7,658 $ 54,484 $ 37,355 Gross realized losses on securities (2,463 ) (3,908 ) (7,431 ) (7,779 ) Net foreign exchange gains (losses) 4,226 6,295 3,801 (175 ) Net realized gains $ 2,106 $ 10,045 $ 50,854 $ 29,401 Net other-than-temporary impairments (1) $ (9,150 ) $ (5,011 ) $ (13,289 ) $ (24,157 ) (1) Other-than-temporary impairments exclude impairment amounts recorded in other comprehensive income under ASC Paragraph 320-10-65-1, which comprise non-credit related amounts on securities that are credit impaired but which management does not intend to sell and it is not more likely than not that Ambac will be required to sell before recovery of the amortized cost basis. Since commencement of the Segregated Account Rehabilitation Proceedings, changes in the estimated timing of claim payments have resulted in adverse changes in projected cash flows on certain impaired Ambac insured securities. Such changes in estimated claim payments on Ambac insured securities contributed to net other-than-temporary impairments for the periods presented in the table above. Further changes to the timing of estimated claim payments could result in additional other-than-temporary impairment charges in the future. Ambac’s other-than-temporary impairments for the three and nine months ended September 30, 2014 also relate to the company’s intent to sell certain securities that were in an unrealized loss position as of the impairment evaluation dates. Future changes in our estimated liquidity needs could result in a determination that Ambac no longer has the ability to hold additional securities that are in an unrealized loss position, which could result in additional other-than-temporary impairment charges. The following table presents a roll-forward of Ambac’s cumulative credit losses on debt securities held as of September 30, 2015 and 2014 for which a portion of an other-than-temporary impairment was recognized in other comprehensive income: Nine Months Ended September 30, 2015 2014 Balance, beginning of period $ 14,062 $ 1,182 Additions for credit impairments recognized on: Securities not previously impaired 7,172 11,337 Securities previously impaired 4,059 — Reductions for credit impairments previously recognized on: Securities that matured or were sold during the period — — Balance, end of period $ 25,293 $ 12,519 Counterparty Collateral, Deposits with Regulators and Other Restrictions: Ambac routinely pledges and receives collateral related to certain business lines and/or transactions. Ambac pledges assets it holds in its investment portfolio to investment agreement and derivative counterparties as collateral. Securities pledged to investment agreement counterparties may not then be re-pledged to another entity. Ambac’s counterparties under derivative agreements have the right to pledge or rehypothecate the securities and as such, these pledged securities are separately classified on the Consolidated Balance Sheets as “Fixed income securities pledged as collateral, at fair value”. The following table presents (i) the sources of collateral either received from various counterparties where Ambac is permitted to sell or re-pledge the collateral or collateral held directly in the investment portfolio and (ii) how that collateral was pledged to various investment agreement, derivative and repurchase agreement counterparties at September 30, 2015 and December 31, 2014 : Fair Value of Cash Fair Value of Cash Fair Value of Cash September 30, 2015: Sources of Collateral: Cash and securities pledged directly from the investment portfolio $ 348,584 $ 108,398 $ 240,186 December 31, 2014: Sources of Collateral: Cash and securities pledged directly from the investment portfolio $ 379,423 $ 156,916 $ 222,507 Securities carried at $6,831 and $6,790 at September 30, 2015 and December 31, 2014 , respectively, were deposited by Ambac Assurance and Everspan with governmental authorities or designated custodian banks as required by laws affecting insurance companies. Securities with fair value of $403,106 as of September 30, 2015 were held by a bankruptcy remote trust to collateralize and fund repayment of debt issued through a re-securitization transaction. The securities may not be sold or repledged by the trust. These assets are held and the secured debt is issued by entities that qualify as VIEs and are consolidated in Ambac’s unaudited consolidated financial statements. Refer to Note 3. Special Purpose Entities, Including Variable Interest Entities ("VIEs") for a further description of this transaction. Guaranteed Securities: Ambac’s fixed income portfolio includes securities covered by guarantees issued by Ambac Assurance and other financial guarantors (“insured securities”). The published rating agency ratings on these securities reflect the higher of the financial strength rating of the financial guarantor or the rating of the underlying issuer. Rating agencies do not always publish separate underlying ratings (those ratings excluding the insurance by the financial guarantor) because the insurance cannot be legally separated from the underlying security by the insurer. In the event these underlying ratings are not available from the rating agencies, Ambac will assign an internal rating. The following table represents the fair value, including the value of the financial guarantee, and weighted-average underlying rating, excluding the financial guarantee, of the insured securities at September 30, 2015 and December 31, 2014 , respectively: Municipal Corporate Mortgage Total Weighted (1) September 30, 2015: Ambac Assurance Corporation (2) $ 53,097 $ — $ 2,119,005 $ 2,172,102 CCC- Assured Guaranty Municipal Corporation 58,794 — — 58,794 A+ National Public Finance Guarantee Corporation 48,695 — — 48,695 A- MBIA Insurance Corporation — 29,108 — 29,108 A+ Total $ 160,586 $ 29,108 $ 2,119,005 $ 2,308,699 CCC December 31, 2014: Ambac Assurance Corporation (2) $ 53,164 $ — $ 2,146,555 $ 2,199,719 CCC- Assured Guaranty Municipal Corporation 119,492 — — 119,492 A National Public Finance Guarantee Corporation 67,895 — — 67,895 A- MBIA Insurance Corporation — 32,460 — 32,460 A+ Total $ 240,551 $ 32,460 $ 2,146,555 $ 2,419,566 CCC (1) Ratings are based on the lower of Standard & Poor’s or Moody’s rating. If unavailable, Ambac’s internal rating is used. (2) Includes asset-backed securities with a fair value of $78,925 and $51,395 at September 30, 2015 and December 31, 2014 , insured by Ambac UK . Investment Income: Net investment income was comprised of the following for the affected periods: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Fixed income securities $ 67,293 $ 84,339 $ 197,506 $ 233,878 Short-term investments 85 832 186 2,000 Loans 113 123 338 415 Investment expense (1,872 ) (2,413 ) (6,801 ) (7,723 ) Securities available-for-sale and short-term 65,619 82,881 191,229 228,570 Other investments (1,424 ) 700 10,702 5,905 Total net investment income $ 64,195 $ 83,581 $ 201,931 $ 234,475 Net investment income from Other investments primarily represents changes in fair value on securities classified as trading or under the fair value option plus, for periods after August 28, 2014, income from Ambac's equity interest in an unconsolidated trust created in connection with its sale of Segregated Account junior surplus notes on that date. The portion of net unrealized gains (losses) related to trading securities still held at the end of each period is as follows: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Net gains (losses) recognized during the period on trading securities $ (2,549 ) $ 329 $ 7,493 $ 5,534 Less: net gains (losses) recognized during the reporting period on trading securities sold during the period 933 — 7,534 (431 ) Unrealized gains (losses)recognized during the reporting period on trading securities still held at the reporting date $ (3,482 ) $ 329 $ (41 ) $ 5,965

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	9. DERIVATIVE INSTRUMENTS The following tables summarize the gross fair values of individual derivative instruments and the impact of legal rights of offset as reported in the Consolidated Balance Sheets as of September 30, 2015 and December 31, 2014 : Gross Gross Net Amounts Gross Net Amount September 30, 2015: Derivative Assets: Credit derivatives $ 1,345 $ — $ 1,345 $ — $ 1,345 Interest rate swaps 153,528 63,785 89,743 — 89,743 Futures contracts — — — — — Total non-VIE derivative assets $ 154,873 $ 63,785 $ 91,088 $ — $ 91,088 Derivative Liabilities: Credit derivatives $ 31,232 $ — $ 31,232 $ — $ 31,232 Interest rate swaps 408,168 63,785 344,383 186,752 157,631 Futures contracts 220 — 220 — 220 Total non-VIE derivative liabilities $ 439,620 $ 63,785 $ 375,835 $ 186,752 $ 189,083 VIE derivative assets: Interest rate swaps $ — $ — $ — $ — $ — Currency swaps 31,429 31,429 — — — Total VIE derivative assets $ 31,429 $ 31,429 $ — $ — $ — VIE derivative liabilities: Interest rate swaps $ 2,065,224 $ — $ 2,065,224 $ — $ 2,065,224 Currency swaps — 31,429 (31,429 ) — (31,429 ) Total VIE derivative liabilities $ 2,065,224 $ 31,429 $ 2,033,795 $ — $ 2,033,795 December 31, 2014: Derivative Assets: Credit derivatives $ 2,043 $ — $ 2,043 $ — $ 2,043 Interest rate swaps 161,640 54,666 106,974 — 106,974 Total non-VIE derivative assets $ 163,683 $ 54,666 $ 109,017 $ — $ 109,017 Derivative Liabilities: Credit derivatives $ 75,502 $ — $ 75,502 $ — $ 75,502 Interest rate swaps 385,546 54,666 330,880 169,573 161,307 Futures contracts 562 — 562 562 — Total non-VIE derivative liabilities $ 461,610 $ 54,666 $ 406,944 $ 170,135 $ 236,809 Variable Interest Entities: Interest rate swaps $ 2,133,268 $ — $ 2,133,268 $ — $ 2,133,268 Currency swaps 66,895 — 66,895 — 66,895 Total VIE derivative liabilities $ 2,200,163 $ — $ 2,200,163 $ — $ 2,200,163 Amounts recognized for the right to reclaim cash collateral or the obligation to return cash collateral are not offset against fair value amounts recognized for derivative instruments on the Consolidated Balance Sheets. The amounts representing the right to reclaim cash collateral and posted margin, recorded in “Other assets” were $175,214 and $158,240 as of September 30, 2015 and December 31, 2014 , respectively. There were no amounts held representing an obligation to return cash collateral as of September 30, 2015 and December 31, 2014 . The following tables summarize the location and amount of gains and losses of derivative contracts in the Consolidated Statements of Total Comprehensive Income for the three and nine months ended September 30, 2015 and 2014 : Location of Gain or (Loss) Recognized in Consolidated Statements of Total Comprehensive Income Amount of Gain or (Loss) Recognized in Consolidated Statement of Total Comprehensive Income Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Financial Guarantee: Credit derivatives Net change in fair value of credit derivatives $ 36,952 $ 7,416 $ 44,746 $ 13,579 Financial Services derivatives products: Interest rate swaps Derivative products (63,044 ) (15,638 ) (48,839 ) (112,995 ) Futures contracts Derivative products (2,039 ) (47 ) (3,019 ) (4,516 ) Total Financial Services derivative products (65,083 ) (15,685 ) (51,858 ) (117,511 ) Variable Interest Entities: Currency swaps Income (loss) on variable interest entities 12,235 17,014 53,552 21,425 Interest rate swaps Income (loss) on variable interest entities (15,793 ) (44,846 ) 68,044 (204,411 ) Total Variable Interest Entities (3,558 ) (27,832 ) 121,596 (182,986 ) Total derivative contracts $ (31,689 ) $ (36,101 ) $ 114,484 $ (286,918 ) Financial Guarantee Credit Derivatives: Credit derivatives, which are privately negotiated contracts, provide the counterparty with credit protection against the occurrence of a specific event such as a payment default or bankruptcy relating to an underlying obligation. Upon a credit event, Ambac is generally required to make payments equal to the difference between the scheduled debt service payment and the actual payment made by the issuer. Substantially all of Ambac’s credit derivative contracts relate to structured finance transactions. Credit derivatives issued are insured by Ambac Assurance. None of the outstanding credit derivative transactions at September 30, 2015 include ratings based collateral-posting triggers or otherwise require Ambac to post collateral regardless of Ambac’s ratings or the size of the mark to market exposure to Ambac. Our outstanding credit derivatives were written on a “pay-as-you-go” basis. Similar to an insurance policy execution, pay-as-you-go provides that Ambac pays interest shortfalls on the referenced transaction as they are incurred on each scheduled payment date, but only pays principal shortfalls upon the earlier of (i) the date on which the assets designated to fund the referenced obligation have been disposed of and (ii) the legal final maturity date of the referenced obligation. Ambac maintains internal credit ratings on its guaranteed obligations, including credit derivative contracts, solely to indicate management’s view of the underlying credit quality of the guaranteed obligations. Independent rating agencies may have assigned different ratings on the credits in Ambac’s portfolio than Ambac’s internal ratings. The following tables summarize the gross principal notional outstanding for CDS contracts, by Ambac rating, for each major category as of September 30, 2015 and December 31, 2014 : CLO Other Total Ambac Rating - September 30, 2015: AAA $ — $ — $ — AA 341,668 233,231 574,899 A — 9,322 9,322 BBB (1) — 469,724 469,724 Below investment grade (2) — 259,852 259,852 Total $ 341,668 $ 972,129 $ 1,313,797 Ambac Rating - December 31, 2014: AAA $ — $ — $ — AA 549,923 217,680 767,603 A — 43,160 43,160 BBB (1) — 448,249 448,249 Below investment grade (2) — 270,747 270,747 Total $ 549,923 $ 979,836 $ 1,529,759 (1) BBB internal ratings reflect bonds which are of medium grade credit quality with adequate capacity to pay interest and repay principal. Certain protective elements and margins may weaken under adverse economic conditions and changing circumstances. These bonds are more likely than higher rated bonds to exhibit unreliable protection levels over all cycles. (2) Below investment grade internal ratings reflect bonds which are of speculative grade credit quality with the adequacy of future margin levels for payment of interest and repayment of principal potentially adversely affected by major ongoing uncertainties or exposure to adverse conditions. The tables below summarize information by major category as of September 30, 2015 and December 31, 2014 : CLO Other Total September 30, 2015: Number of CDS transactions 5 9 14 Gross principal notional outstanding $ 341,668 $ 972,129 $ 1,313,797 Net derivative liabilities at fair value $ 1,740 $ 28,147 $ 29,887 December 31, 2014: Number of CDS transactions 6 10 16 Gross principal notional outstanding $ 549,923 $ 979,836 $ 1,529,759 Net derivative liabilities at fair value $ 2,027 $ 71,432 $ 73,459 The maximum potential amount of future payments under Ambac’s credit derivative contracts is generally the gross principal notional outstanding amount included in the above table plus future interest payments payable by the derivative reference obligations. Since Ambac’s credit derivatives typically reference obligations of or assets held by special purpose entities that meet the definition of a VIE, the amount of maximum potential future payments for credit derivatives is included in the table in Note 3. Special Purpose Entities, Including Variable Interest Entities ("VIEs") . Changes in fair value of Ambac’s credit derivative contracts are accounted for at fair value since they do not qualify for the financial guarantee scope exception under the Derivatives and Hedging Topic of the ASC. Changes in fair value are recorded in “Net change in fair value of credit derivatives” on the Consolidated Statements of Total Comprehensive Income (Loss). Although CDS contracts are accounted for at fair value, they are surveilled similar to non-derivative financial guarantee contracts. As with financial guarantee insurance policies, Ambac’s risk group tracks credit migration of CDS contracts’ reference obligations from period to period. Adversely classified credits are assigned risk classifications by the risk group. As of September 30, 2015 , there are four CDS contracts on Ambac’s adversely classified credit listing, with a net derivative liability fair value of $14,958 and gross notional principal outstanding of $259,852 . As of December 31, 2014 , there were four CDS contracts on Ambac’s adversely classified credit listing, with a net derivative liability fair value of $60,729 and total notional principal outstanding of $270,747 . Financial Services Derivative Products: Ambac, through its subsidiary Ambac Financial Services (“AFS”), provides interest rate swaps to states, municipalities and their authorities, asset-backed issuers and other entities in connection with their financings. AFS manages its interest rate swaps business with the goal of retaining some basis risk and excess interest rate sensitivity as an economic hedge against the effects of rising interest rates elsewhere in the Company, including on Ambac’s financial guarantee exposures. As of September 30, 2015 and December 31, 2014 the notional amounts of AFS’s trading derivative products are as follows: Notional Type of derivative September 30, December 31, Interest rate swaps—receive-fixed/pay-variable $ 757,135 $ 782,904 Interest rate swaps—pay-fixed/receive-variable 1,446,248 1,479,650 Interest rate swaps—basis swaps 38,965 55,800 Futures contracts 75,000 80,000 Derivatives of Consolidated Variable Interest Entities Certain VIEs consolidated under the Consolidation Topic of the ASC entered into derivative contracts to meet specified purposes within the securitization structure. The notional for VIE derivatives outstanding as of September 30, 2015 and December 31, 2014 are as follows: Notional Type of VIE derivative September 30, December 31, Interest rate swaps—receive-fixed/pay-variable $ 1,659,640 $ 1,710,344 Interest rate swaps—pay-fixed/receive-variable 3,058,644 3,152,090 Currency swaps 378,050 724,656 Credit derivatives 16,035 18,278 Contingent Features in Derivatives Related to Ambac Credit Risk Ambac’s interest rate swaps with professional swap-dealer counterparties and certain front-end counterparties are generally executed under standardized derivative documents including collateral support and master netting agreements. Under these agreements, Ambac is required to post collateral in the event net unrealized losses exceed predetermined threshold levels. Additionally, given that Ambac Assurance is no longer rated by an independent rating agency, counterparties have the right to terminate the swap positions. As of September 30, 2015 and December 31, 2014 , the net liability fair value of all derivative instruments with contingent features linked to Ambac’s own credit risk was $101,698 and $92,869 , respectively, related to which Ambac had posted assets as collateral with a fair value of $153,901 and $118,844 , respectively. All such ratings-based contingent features have been triggered as requiring maximum collateral levels to be posted by Ambac while preserving counterparties’ rights to terminate the contracts. Assuming all contracts terminated on September 30, 2015 , settlement of collateral balances and net derivative liabilities would result in a net receipt of cash and/or securities by Ambac. If counterparties elect to exercise their right to terminate, the actual termination payment amounts will be determined in accordance with derivative contract terms, which may result in amounts that differ from market values as reported in Ambac’s financial statements.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	10. INCOME TAXES Ambac files a consolidated Federal income tax return with its subsidiaries. Ambac and its subsidiaries also file separate or combined income tax returns in various states, local and foreign jurisdictions. The following are the major jurisdictions in which Ambac and its subsidiaries operate and the earliest tax years subject to examination: Jurisdiction Tax Year United States 2010 New York State 2011 New York City 2011 United Kingdom 2009 Italy 2009 As of September 30, 2015 Ambac had loss carryforwards totaling $4,831,481 . This includes carryforwards of $143,491 relating to U.S. capital losses, $91,863 of Ambac UK loss carryforwards, and an ordinary U.S. federal net operating tax carryforward of approximately $4,596,127 , which, if not utilized, will begin expiring in 2029 , and will fully expire in 2034 . The tax effects of temporary differences that give rise to significant portions of the deferred tax liabilities and deferred tax assets at September 30, 2015 and December 31, 2014 are presented below: September 30, December 31, Deferred tax liabilities: Insurance intangible $ 447,807 $ 493,822 Variable interest entities 15,615 14,149 Investments 147,881 138,072 Unearned premiums and credit fees 99,372 104,589 Other 33,768 33,835 Total deferred tax liabilities 744,443 784,467 Deferred tax assets: Net operating loss and capital carryforward 1,691,018 1,890,551 Loss reserves 119,427 185,881 Compensation 6,016 5,276 AMT Credits 18,439 10,359 Other 9,540 9,539 Sub total deferred tax assets 1,844,440 2,101,606 Valuation allowance 1,101,954 1,319,218 Total deferred tax assets 742,486 782,388 Net deferred tax asset (liability) $ (1,957 ) $ (2,079 ) In accordance with the Income Tax Topic of the ASC, a valuation allowance is recognized if, based on the weight of available evidence, it is more-likely-than-not that some, or all, of the deferred tax asset will not be realized. As a result of the risks and uncertainties associated with future operating results, management believes it is more likely than not that the Company will not generate sufficient taxable income to recover the deferred tax operating asset and therefore has a full valuation allowance.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. COMMITMENTS AND CONTINGENCIES The following commitments and contingencies provide an update of those discussed in Note 18: Commitments and Contingencies in the Notes to Consolidated Financial Statements included Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 , and should be read in conjunction with the complete descriptions provided in the aforementioned Form 10-K. Ambac is responsible for leases on the rental of office space. The executive office of Ambac is located in New York City under a lease agreement that was modified in September 2015 and extended in October 2015 to allow Ambac to remain in the same office space through September 2019 and on one floor through the end of 2029, with an option to continue to occupy other currently leased floors through the end of 2029. Rent payment under this lease made through September 2019 will result in the periodic reduction of Segregated Account Junior Surplus Notes that were previously issued to the landlord. Ambac leases additional space for its data center, disaster recovery site and for its international locations under lease agreements that expire periodically through October 2020. An estimate of future net minimum lease payments in each of the next five years ending December 31, and the periods thereafter, is as follows: 2015 (1) 2016 2017 2018 2019 Thereafter Total Operating lease obligations $ 1,375 $ 6,168 $ 6,168 $ 6,168 $ 5,046 $ 14,947 $ 39,872 (1) Includes October through December 2015 The Segregated Account and Wisconsin Rehabilitation Proceeding On February 27, 2015, the Bank of New York Mellon Trust Company, N.A., as trustee, made a motion for allowance of a policy claim that had been disallowed by the Rehabilitator. The Rehabilitator opposed the motion on March 23, 2015 and the trustee filed a reply in further support of its motion on March 26, 2015. On April 6, 2015, the Rehabilitation Court denied the trustee’s motion. On March 18, 2015, the Rehabilitator filed a motion to confirm and declare the reimbursement amounts due with respect to cash claim payments made by Ambac Assurance and the Segregated Account on a certain policy. Objections to the motion were due on April 27, 2015, but no objection was filed. On May 1, 2015, the Rehabilitation Court granted the Rehabilitator’s motion. Litigation Against Ambac County of Alameda et al. v. Ambac Assurance Corporation et al. (Superior Court of the State of California, County of San Francisco, second amended complaint filed on or about August 23, 2011); Contra Costa County et al. v. Ambac Assurance Corporation et al. (Superior Court of the State of California, County of San Francisco, third amended complaint filed on or about October 21, 2011); The Olympic Club v. Ambac Assurance Corporation et al. (Superior Court of the State of California, County of San Francisco, fourth amended complaint filed on or about October 21, 2011). Ambac Assurance and the other Bond Insurer Defendants filed a demurrer seeking dismissal of the current amended complaints on September 21, 2011, which was denied on October 20, 2011. On December 2, 2011, Ambac Assurance and the other Bond Insurer Defendants filed a special motion to strike the current amended complaints under California’s Anti-SLAPP statute (Calif. Code of Civ. Proc. Section 425.16). A hearing on the motion was held on March 23, 2012. On May 1, 2012, the Court ruled that the complaints were governed by the Anti-SLAPP statute to the extent they alleged conspiracy to influence the rating agencies’ rating methodologies, but not to the extent that the complaints alleged false or misleading statements or nondisclosures. After oral argument on March 21, 2013, the court dismissed claims related to the conspiracy branch of the complaint under the California Antitrust Law (the Cartwright Act) and after oral argument on April 22, 2013 denied defendants’ motion to dismiss claims under the California Unfair Competition Law. The court entered an order to this effect on July 9, 2013. On September 9, 2013, plaintiffs filed a notice of appeal of the July 9th order and on September 30, 2013, Ambac Assurance filed a notice of cross-appeal. On September 9, 2013, the parties filed motions for attorneys’ fees in connection with the portions of the Anti-SLAPP motions on which they were successful. The court denied plaintiffs’ motion for fees from the bench on November 8, 2013. On March 26, 2014, the court granted the defendants’ motions for attorneys’ fees awarding Ambac Assurance approximately $207 . The court’s decisions on attorneys’ fees were memorialized in an order initially entered on March 26, 2014 and amended on May 8, 2014. On July 7, 2014, plaintiffs filed a notice of appeal from the court’s amended order awarding attorneys’ fees to Ambac Assurance and the other defendants and denying fees to plaintiffs. This appeal was dismissed on December 19, 2014. Plaintiffs have filed a motion to reinstate the appeal, stating that it should only have been dismissed as against one defendant with whom plaintiffs settled. Ambac did not oppose that motion, which was granted on January 29, 2015. Also on July 7, 2014, the Bond Insurer Defendants filed their appellate brief appealing the July 9th Order. Plaintiffs’ opposition to the Bond Insurer Defendants’ appellate brief and plaintiffs’ affirmative brief on their cross-motion were filed on November 5, 2014. The defendants’ brief in opposition to plaintiffs’ appeal and in further support of their cross-appeal was filed on February 3, 2015. Plaintiffs’ reply brief in further support of their appeal was filed on April 24, 2015. The appeal is now fully briefed and awaiting scheduling of oral argument. On July 2, 2015, plaintiffs filed an appeal brief seeking to overturn the Court’s May 8, 2014 amended Order awarding defendants attorneys’ fees and denying an award of attorneys’ fees to plaintiffs . On August 7, 2015, defendants filed a motion to dismiss that appeal insofar as it seeks to reverse the court’s order denying plaintiffs an award of attorneys’ fees. The Court denied that motion. The Bond Insurer Defendants filed their appellate brief in opposition to plaintiffs’ appeal of the Court’s May 8, 2014 order on October 19, 2015. City of New Orleans v. Ambac Assurance Corporation, Ambac Financial Services, LLC, PaineWebber Capital Services, Inc. and UBS Securities LLC (United States District Court, Eastern District of Louisiana, Civil Action No. 08-3949 filed on July 17, 2008). This action was brought by the City of New Orleans ("New Orleans") against Ambac Assurance and Ambac Financial Services on July 17, 2008 in connection with their participation in a New Orleans bond issue. New Orleans issued variable rate demand obligations ("VRDOs"), which were insured by Ambac Assurance, and entered into an interest rate swap agreement with PaineWebber, Inc. in order to fix its interest rate on the VRDOs. PaineWebber in turn entered into an interest rate swap agreement with Ambac Financial Services with terms that mirrored those of the New Orleans/Paine Webber swap. On December 23, 2009, New Orleans filed an Amended Complaint alleging that Ambac Assurance failed to provide credit enhancement as a result of Ambac Assurance's rating being downgraded by the rating agencies in 2008, and seeking damages against Ambac Assurance and Ambac Financial Services for the following causes of action: (1) breach of contract for credit enhancement, (2) unjust enrichment, (3) error in the principal cause, (4) fraud in the inducement of contract, (5) negligent misrepresentation, (6) bad faith, (7) breach of the swap, (8) tortious interference with the swap, (9) breach of and tortious interference with remarketing agreement and (10) detrimental reliance. On October 14, 2010, the Court granted a motion to dismiss all claims against Ambac Assurance and Ambac Financial Services and in late 2011, administratively closed the case and gave New Orleans 180 days to settle or move to re-open the case. In 2014, New Orleans filed a motion to re-open the case as to UBS Securities LLC, which the Court granted. New Orleans and UBS Securities LLC entered into a settlement agreement, and on May 20, 2015, the Court entered a final order and judgment dismissing with prejudice the case against all defendants. The City is appealing the District Court's October 14, 2010 decision to the United States Court of Appeals for the Fifth Circuit and on September 8, 2015 filed its appellate brief. Ambac Assurance’s estimates of projected losses for RMBS transactions consider, among other things, the RMBS transactions’ payment waterfall structure, including the application of interest and principal payments and recoveries, and depend in part on our interpretations of contracts and other bases of our legal rights. From time to time, bond trustees and other transaction participants have employed different contractual interpretations. It is not possible to predict whether disputes will arise, nor the outcomes of any potential litigation. It is possible that there could be unfavorable outcomes in disputes or proceedings and that our interpretations may prove to be incorrect, which could lead to changes to our estimate of loss reserves. Ambac Assurance has periodically received various regulatory inquiries and requests for information with respect to investigations and inquiries that such regulators are conducting. Ambac Assurance has complied with all such inquiries and requests for information. It is not reasonably possible to predict whether additional suits will be filed or whether additional inquiries or requests for information will be made, and it is also not possible to predict the outcome of litigation, inquiries or requests for information. It is possible that there could be unfavorable outcomes in these or other proceedings. Legal accruals for litigation against Ambac which are probable and reasonably estimable, and management's estimated range of loss for such matters, are not material to the operating results or financial position of the Company. For the litigation matters Ambac is defending that do not meet the “probable and reasonably estimable” accrual threshold and where no loss estimates have been provided above, management is unable to make a meaningful estimate of the amount or range of loss that could result from unfavorable outcomes but, under some circumstances, adverse results in any such proceedings could be material to our business, operations, financial position, profitability or cash flows. The Company believes that it has substantial defenses to the claims above and, to the extent that these actions proceed, the Company intends to defend itself vigorously; however, the Company is not able to predict the outcomes of these actions. Litigation Filed by Ambac In the ordinary course of their businesses, certain of Ambac’s subsidiaries assert claims in legal proceedings against third parties to recover losses already paid and/or mitigate future losses. The amounts recovered and/or losses avoided which may result from these proceedings is uncertain, although recoveries and/or losses avoided in any one or more of these proceedings during any quarter or fiscal year could be material to Ambac’s results of operations in that quarter or fiscal year. Ambac Assurance Corporation v. Adelanto Public Utility Authority (United States District Court, Southern District of New York, filed on June 1, 2009). On December 23, 2014, the parties entered into a Judgment Satisfaction and Release Agreement to resolve the matter and in April 2015, when the Agreement became fully effective, the parties dismissed the Authority’s appeal to the Court of Appeals for the Second Circuit and the portion of the action that remained in the District Court and filed instruments of satisfaction of Ambac’s judgment against the Authority in the Southern District of New York and the Central District of California. Ambac Assurance received approximately $7,760 in satisfaction of its judgment against the Authority. Erste Europäische Pfandbriefund Kommunalkreditbank AG In Luxemburg and Ambac Assurance Corporation v. City of San Bernardino, California (United States Bankruptcy Court, Central District of California, Riverside Division, filed on January 7, 2015). On March 13, 2015, the City filed a motion to dismiss the complaint, which plaintiffs opposed. On May 11, 2015, the court heard oral argument and granted the City’s motion to dismiss. On June 8, 2015, plaintiffs filed a notice of appeal of the court’s order granting the City’s motion to dismiss with the Bankruptcy Appellate Panel for the Ninth Circuit, and their appellate brief is due on or before January 5, 2016. Ambac UK v. J.P. Morgan Investment Management (Supreme Court of the State of New York, County of New York, filed May 4, 2009, No. 650259/2009). Ambac UK commenced this action against J.P. Morgan Investment Management asserting claims for breach of contract, breach of fiduciary duty and gross negligence relating to defendant’s mismanagement of assets supporting bonds issued by Ballantyne Plc and insured by Ambac UK that funded excess reserves for term life insurance required by regulation. (Pursuant to an agreement with Ballantyne Plc, Ambac UK was given the authority to prosecute Ballantyne plc's claims against J.P. Morgan Investment Management.) On March 24, 2010, the court granted defendant's motion to dismiss the complaint. Ambac UK appealed the March 2010 decision and on July 14, 2011, the Appellate Division for the First Department reversed the decision and reinstated Ambac UK's claims in their entirety. Fact discovery was completed on August 13, 2015. Expert discovery is ongoing. In connection with Ambac Assurance’s efforts to seek redress for breaches of representations and warranties and fraud related to the information provided by both the underwriters and the sponsors of various RMBS transactions and for failure to comply with the obligation by the sponsors to repurchase ineligible loans, Ambac Assurance has filed various lawsuits: • Ambac Assurance Corporation v. EMC Mortgage LLC (formerly known as EMC Mortgage Corporation), J.P. Morgan Securities, Inc. (formerly known as Bear, Stearns & Co. Inc.), and JP Morgan Chase Bank, N.A. (Supreme Court of the State of New York, County of New York, filed February 17, 2011). On December 18, 2014, defendants filed a motion for partial summary judgment seeking to dismiss the plaintiffs’ claim for fraudulent inducement arguing that as a matter of law, plaintiffs cannot prove justifiable reliance. Ambac Assurance has opposed the motion, which is fully briefed. The court heard oral argument on July 14, 2015. No decision has been issued. • Ambac Assurance Corporation and The Segregated Account of Ambac Assurance Corporation v. EMC Mortgage LLC (formerly known as EMC Mortgage Corporation), J.P. Morgan Securities, Inc. (formerly known as Bear, Stearns & Co. Inc.), and JP Morgan Chase Bank, N.A. (Supreme Court of the State of New York, County of New York, filed March 30, 2012 and amended on August 14, 2012). On June 13, 2013, the court dismissed Ambac Assurance’s contractual claims but not its claims for fraudulent inducement or successor liability. Ambac Assurance appealed the trial court’s decision. On October 16, 2014, the Appellate Division for the First Department affirmed the trial court’s dismissal. In November 2014, Ambac Assurance filed a motion for leave to re-argue, or in the alternative to appeal, the decision. Defendants opposed the motion. On May 14, 2015, the First Department denied the motion. With respect to the claims that remain in the case, discovery is ongoing. • Ambac Assurance Corporation and The Segregated Account of Ambac Assurance Corporation v. Countrywide Securities Corp., Countrywide Financial Corp. (a.k.a. Bank of America Home Loans) and Bank of America Corp. (Supreme Court of the State of New York, County of New York, filed on September 28, 2010). On May 1, 2015, Ambac Assurance filed motions for partial summary judgment, which defendants opposed. Defendants also each filed motions for summary judgment, which Ambac Assurance opposed. The court heard oral argument on July 15, 2015. On October 27, 2015, the court issued a decision granting in part and denying in part the parties’ respective summary judgment motions regarding Ambac Assurance’s claims against Countrywide, and issued a second decision granting Ambac Assurance’s partial motion for summary judgment and denying Bank of America’s motion for summary judgment regarding Ambac Assurance’s secondary-liability claims against Bank of America. Ambac Assurance has filed a notice of appeal from the former decision. • Ambac Assurance Corporation and The Segregated Account of Ambac Assurance Corporation v. Nomura Credit & Capital, Inc. and Nomura Holding America Inc. (Supreme Court of the State of New York, County of New York, filed on April 15, 2013). On July 12, 2013 defendants filed a motion to dismiss Ambac’s initial complaint which alleged claims for material breach of contract and for the repurchase of loans that breach representations and warranties under the contracts. Ambac opposed the motion. The court held oral argument on November 13, 2013. On September 22, 2014, plaintiffs filed an amended complaint alleging claims for fraudulent inducement, material breach of contract and for the repurchase of loans that breach representations and warranties under the contracts, as well as damages. On October 31, 2014 defendants filed a motion to strike the amended complaint. Ambac Assurance opposed that motion and at the court’s recommendation also filed a cross motion for leave to amend the complaint on November 14, 2014, which the defendants opposed. Defendants also filed a motion to dismiss the fraudulent inducement claim, which Ambac Assurance opposed. All motions are fully briefed. The court heard oral argument on the defendants’ motion to dismiss the fraudulent inducement claim on April 14, 2015. On June 3, 2015, the court denied defendants’ July 2013 motion to dismiss Ambac’s claim for breaches of representations and warranties, but granted the defendants’ motion to dismiss Ambac’s claims for breach of the repurchase protocol and for alter ego liability against Nomura Holding. • The Segregated Account of Ambac Assurance Corporation and Ambac Assurance Corporation v. Countrywide Home Loans, Inc. (Wisconsin Circuit Court for Dane County, filed on December 30, 2014) (the “Wisconsin Action”). Ambac Assurance alleges a claim for fraudulent inducement in connection with Ambac Assurance’s issuance of insurance policies relating to five residential mortgage-backed securitizations that are not the subject of Ambac Assurance’s previously filed lawsuit against the same defendant. Defendant filed a motion to dismiss the complaint on February 20, 2015, which Ambac Assurance opposed. The court heard oral argument on two of Countrywide’s grounds for dismissal on June 23, 2015, and indicated that it would dismiss the Wisconsin Action without prejudice for lack of personal jurisdiction. The court issued an order to that effect on July 2, 2015. Ambac Assurance is appealing the July 2, 2015 order, and on September 30, 2015, filed its opening appeal brief. Countrywide filed its opposition to that appeal on October 30, 2015. On June 30, 2015, plaintiffs filed a Summons with Notice in the Supreme Court of the State of New York, County of New York, No. 652321/15 (the “2015 New York Action”), alleging claims identical to the Wisconsin Action. On July 21, 2015, plaintiffs filed a complaint in the 2015 New York Action and a motion to stay the 2015 New York Action pending appeal and litigation of the Wisconsin Action. On August 5, 2015, Countrywide filed its opposition to plaintiffs’ motion to stay and on August 10, 2015, Countrywide filed a motion to dismiss the complaint, which Ambac opposed. The motions are fully briefed and no decisions have been issued. • Ambac Assurance Corporation and the Segregated Account of Ambac Assurance Corporation v. Countrywide Home Loans, Inc., Countrywide Securities Corp., Countrywide Financial Corp., and Bank of America Corp. (Supreme Court of the State of New York, County of New York, filed on December 30, 2014). Ambac Assurance alleges a claim for fraudulent inducement in connection with Ambac Assurance’s issuance of insurance policies relating to eight residential mortgage-backed securitizations that are not the subject of Ambac Assurance’s previously filed lawsuits against the same defendants, and asserts successor liability and alter ego claims against Bank of America. On February 20, 2015, the Countrywide defendants filed a motion to dismiss the complaint, which Bank of America joined on February 23, 2015. Ambac Assurance opposed the motion. The motion is fully briefed and no decision has been issued.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Segment Information	12. SEGMENT INFORMATION Ambac has two reportable business segments, as follows: (i) Financial Guarantee, which provides financial guarantees (including credit derivatives) for public finance, structured finance and international obligations; and (ii) Financial Services, which provides investment agreements, funding conduits, interest rate swaps, principally to clients of the financial guarantee business. Ambac’s reportable business segments are strategic business units that offer different products and services. They are managed separately because each business required different marketing strategies, personnel skill sets and technology. Ambac Assurance guarantees the swap and investment agreement obligations of its Financial Services subsidiaries. Additionally, Ambac Assurance provides loans to the Financial Services businesses. Inter-segment revenues include the premiums and investment income earned under those agreements. Information provided below for unaffiliated “Corporate and Other” primarily relates to investment income on Ambac's investment portfolio. Equity in net income of investees accounted for by the equity method relates to the Owner Trust Certificate received when Ambac deposited its Segregated Account junior surplus note into a Trust (see Note 1. Background and Business Description in the Notes to Consolidated Financial Statements included Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 for further information relating to the sale by Ambac of a junior surplus note issued to it by the Segregated Account). Inter-segment for "Corporate and Other" relates to amounts received by Ambac under the Mediation Agreement dated September 21, 2011 (as more fully described in Note 1. Background and Business Description in the Notes to Consolidated Financial Statements included Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 ), including accrual of interest on the junior surplus note issued by the Segregated Account prior to Ambac's sale of the note. The following table is a summary of financial information by reportable business segment for the affected periods: Financial Financial Corporate Inter-segment Consolidated Three Months Ended September 30, 2015: Revenues: Unaffiliated customers (1) $ 152,024 $ (66,997 ) $ 1,538 $ — $ 86,565 Equity in net income of investees accounted for by equity method — — 1,125 — 1,125 Inter-segment 24 (204 ) 252 (72 ) — Total revenues before expenses and reorganization items 152,048 (67,201 ) 2,915 (72 ) 87,690 Pre-tax income (loss): Unaffiliated customers (1)(2)(3) (320,414 ) (67,655 ) (1,249 ) — (389,318 ) Equity in net income of investees accounted for by equity method — — 1,125 — 1,125 Inter-segment (763 ) 425 1,302 (964 ) — Pre-tax income (loss) (321,177 ) (67,230 ) 1,178 (964 ) (388,193 ) Total assets as of September 30, 2015 23,610,582 363,118 289,238 3,981 24,266,919 Net investment income 61,292 139 2,764 — 64,195 Insurance intangible amortization 39,680 — — — 39,680 Interest expense 29,738 161 — — 29,899 Goodwill impairment 514,511 — — — 514,511 Three Months Ended September 30, 2014: Revenues: Unaffiliated customers (1) $ 170,335 $ (15,445 ) $ 78 $ — $ 154,968 Equity in net income of investees accounted for by equity method — — 371 — 371 Inter-segment 237 (219 ) 5,838 (5,856 ) — Total revenues before expenses and reorganization items 170,572 (15,664 ) 6,287 (5,856 ) 155,339 Pre-tax income (loss): Unaffiliated customers (1) (2) (3) 101,975 (16,304 ) (1,269 ) — 84,402 Equity in net income of investees accounted for by equity method — — 371 — 371 Inter-segment (6,441 ) (281 ) 6,722 — — Pre-tax income (loss) 95,534 (16,585 ) 5,824 — 84,773 Total assets as of September 30, 2014 25,926,306 349,411 298,873 16,195 26,590,785 Net investment income 82,978 154 449 — 83,581 Insurance intangible amortization 41,908 — — — 41,908 Interest expense 31,491 350 — — 31,841 (1) Included in both revenues from unaffiliated customers and in pre-tax income (loss) from unaffiliated customers is net investment income. (2) Included in pre-tax income (loss) from unaffiliated customers is interest expense. (3) Included in pre-tax income (loss) from unaffiliated customers is amortization of intangible asset and impairment of goodwill. Such assets were established upon the adoption of Fresh Start on April 30, 2013. Financial Financial Corporate Inter-segment Consolidated Nine Months Ended September 30, 2015: Revenues: Unaffiliated customers (1) $ 521,340 $ (53,566 ) $ 2,951 $ — $ 470,725 Equity in net income of investees accounted for by equity method — — 3,208 — 3,208 Inter-segment 286 (565 ) 388 (109 ) — Total revenues before expenses and reorganization items 521,626 (54,131 ) 6,547 (109 ) 473,933 Pre-tax income (loss): Unaffiliated customers (1)(2)(3) 172,271 (55,861 ) (5,136 ) — 111,274 Equity in net income of investees accounted for by equity method — — 3,208 — 3,208 Inter-segment (2,087 ) (139 ) 3,027 (801 ) — Pre-tax income (loss) 170,184 (56,000 ) 1,099 (801 ) 114,482 Total assets as of September 30, 2015 23,610,582 363,118 289,238 3,981 24,266,919 Net investment income 195,270 401 6,260 — 201,931 Insurance intangible amortization 115,200 — — — 115,200 Interest expense 85,165 815 — — 85,980 Goodwill impairment 514,511 — — — 514,511 Nine Months Ended September 30, 2014: Revenues: Unaffiliated customers (1) $ 437,591 $ (116,294 ) $ 142 $ — $ 321,439 Equity in net income of investees accounted for by equity method — — 371 — 371 Inter-segment 937 (901 ) 23,309 (23,345 ) — Total revenues before expenses and reorganization items 438,528 (117,195 ) 23,822 (23,345 ) 321,810 Pre-tax income (loss): Unaffiliated customers (1) (2) (3) 157,551 (119,287 ) (4,976 ) — 33,288 Equity in net income of investees accounted for by equity method — — 371 — 371 Inter-segment (24,995 ) (1,150 ) 26,145 — — Pre-tax income (loss) 132,556 (120,437 ) 21,540 — 33,659 Total assets as of September 30, 2014 25,926,306 349,411 298,873 16,195 26,590,785 Net investment income 232,995 967 513 — 234,475 Insurance intangible amortization 109,878 — — — 109,878 Interest expense 94,886 1,236 — — 96,122 (1) Included in both revenues from unaffiliated customers and in pre-tax income (loss) from unaffiliated customers is net investment income. (2) Included in pre-tax income (loss) from unaffiliated customers is interest expense. (3) Included in pre-tax income (loss) from unaffiliated customers is amortization of intangible asset and impairment of goodwill. Such assets were established upon the adoption of Fresh Start on April 30, 2013. The following table summarizes gross premiums written, net premiums earned and the net change in fair value of credit derivatives included in the Financial Guarantee segment by location of risk for the affected periods: Three Months Ended September 30, 2015 Three Months Ended September 30, 2014 Gross Net Net Change in Gross Net Net Change in United States $ (2,386 ) $ 60,402 $ 30,604 $ (15,355 ) $ 44,882 $ 262 United Kingdom 260 8,081 — 1,482 14,309 — Other international (6,584 ) 3,052 6,348 173 5,640 7,154 Total $ (8,710 ) $ 71,535 $ 36,952 $ (13,700 ) $ 64,831 $ 7,416 Nine Months Ended September 30, 2015 Nine Months Ended September 30, 2014 Gross Net Net Change in Gross Net Net Change in United States $ (5,172 ) $ 163,094 $ 39,286 $ (44,266 ) $ 141,472 $ 6,283 United Kingdom 7,295 23,659 — (1,681 ) 55,752 — Other international (20,963 ) 11,379 5,460 (19,005 ) 15,167 7,296 Total $ (18,840 ) $ 198,132 $ 44,746 $ (64,952 ) $ 212,391 $ 13,579

Basis of Presentation and Sig20

Basis of Presentation and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies [Text Block]	Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles ("GAAP") for interim financial reporting and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by GAAP for annual periods. These financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in the Annual Report on Form 10-K for the year ended December 31, 2014 . The accompanying consolidated financial statements have not been audited by an independent registered public accounting firm in accordance with the standards of the Public Company Accounting Oversight Board (U.S.), but in the opinion of management such financial statements include all adjustments, consisting only of normal recurring adjustments, necessary for the fair statement of the Company’s consolidated financial position and results of operations. All intercompany balances and transactions have been eliminated. The results of operations for the three and nine months ended September 30, 2015 may not be indicative of the results that may be expected for the year ending December 31, 2015 . The December 31, 2014 consolidated balance sheet was derived from audited financial statements. The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. As additional information becomes available or actual amounts become determinable, the recorded estimates are revised and reflected in operating results.
Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]	Goodwill: At the Fresh Start Reporting Date, we revalued our assets and liabilities to current estimated fair value. The excess reorganization value which could not be attributed to the fair value of specific identified tangible and intangible assets ("fair value of net assets") was recorded as goodwill. Pursuant to the Intangibles - Goodwill and Other Topic of the ASC, goodwill is not amortized but is subject to annual impairment testing. We test goodwill for impairment as of October 1 st of each year. Goodwill is also tested more frequently if indicators of impairment exist for each reporting unit. The Company has an option to first assess qualitative factors, in their totality, to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount as a basis for determining whether it is necessary to perform a goodwill impairment test. If the Company determines that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, then the Company is required to perform the goodwill impairment test. Alternatively, we may bypass this qualitative assessment and perform step one of the goodwill impairment test described below. Goodwill impairment is determined using a two-step approach. In step one of the goodwill impairment test, the fair value of a reporting unit is compared with its carrying amount, including goodwill. If the fair value is in excess of the carrying amount, including goodwill, the reporting unit’s goodwill is considered not to be impaired. If the carrying amount, including goodwill, of a reporting unit exceeds its fair value, the second step of the goodwill impairment test is performed to measure the amount of impairment loss, if any. In step two of the goodwill impairment test, the implied fair value of a reporting unit’s goodwill is compared with the carrying amount of that goodwill. The implied fair value of goodwill is determined in the same manner as the amount of goodwill recognized in a business combination and is defined as the excess of the fair value of a reporting unit over the fair value of the net assets of a reporting unit. If the carrying amount of goodwill exceeds its implied fair value, an impairment loss is recognized for the excess. If the carrying amount of goodwill is less than its implied fair value, no goodwill impairment is recognized. Goodwill impairment testing is performed at the reporting unit level. We have identified two reporting units of Ambac: (1) Financial Guarantee, which provides financial guarantees (including credit derivatives) for public finance, structured finance and other obligations; and (2) Financial Services, which provides investment agreements, funding conduits, and interest rate swaps, principally to clients of the financial guarantee business. These reporting units are also the sole operating segments which make up the Financial Guarantee and Financial Services reportable segments, respectively, as further described in Note 19. Segment Information in the Notes to Consolidated Financial Statements included Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 . We have assigned assets and liabilities to each reporting unit based on specific identification. In evaluating which reporting units should be assigned goodwill, we considered the sources of Ambac’s estimated enterprise value at the Fresh Start Reporting Date, as further described in Note 3. Fresh Start Financial Statement Reporting in the Notes to Consolidated Financial Statements included Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 . Based on that analysis, we have assigned all goodwill recorded at the Fresh Start Reporting Date to the Financial Guarantee reporting unit. During the September 30, 2015 reporting period, Ambac determined sufficient indicators of potential impairment existed to perform an interim goodwill impairment evaluation for the Financial Guarantee reporting unit. These indicators included the recent trading values of Ambac stock and changes in Ambac credit spreads. In conducting the goodwill impairment analysis as of September 30, 2015 , we performed step one of the goodwill impairment test for the Financial Guarantee reporting unit. We estimated the fair value of the Financial Guarantee reporting unit using a market approach, which is derived using: i) Ambac’s common stock and warrant market capitalization, ii) fair value estimates of Ambac Assurance preferred shares (reported as noncontrolling interests on Ambac's balance sheet) and iii) an estimated control premium. Step one of the impairment test indicated the Financial Guarantee reporting unit's carrying value exceeded its fair value. Accordingly, the Company performed step two of the impairment test as of September 30, 2015 , which indicated the implied fair value of goodwill was zero. This was the result of substantial decreases in the Financial Guarantee reporting unit's fair value and substantial increases in the fair value of its net assets. The fair value of the Financial Guarantee reporting unit decreased significantly due to a material decrease in Ambac's market capitalization components (described above). The Financial Guarantee reporting unit's fair value of net assets increased significantly primarily as a result of a decrease in the estimated fair value of financial guarantee liabilities and, to a lesser extent, a decrease in the fair value of long-term debt. The fair value decrease in financial guarantee liabilities, which is a Level 3 estimate, was primarily driven by wider Ambac credit spreads and positive loss and loss expense reserves development. Please refer to Note 7. Fair Value Measurements for further discussion on the fair value model for financial guarantee liabilities. The fair value decrease in long-term debt was driven by lower market pricing on surplus notes and junior surplus notes. As a result, the Company recorded a full non-cash, non-tax deductible goodwill impairment charge of $514,511 million at September 30, 2015. The following is a summary of activity in goodwill for the Financial Guarantee reporting unit: Nine Months Ended September 30, 2015 Year Ended December 31, 2014 Beginning balance $ 514,511 $ 514,511 Impairment loss (514,511 ) — Ending balance $ — $ 514,511
Reclassifications	Reclassifications Certain reclassifications have been made to prior years' amounts to conform to the current year's presentation.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Adopted and Recently Issued Accounting Standards Adopted: Effective January 1, 2015, Ambac adopted ASU 2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360) - Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity . The objective of this ASU is to limit discontinued operations reporting to disposals of components of an entity that represent strategic shifts that have (or will have) a major effect on an entity's operations and financial results. Under previous U.S. GAAP, many disposals, some of which may be routine in nature and not a change in an entity's strategy, were reported in discontinued operations. The ASU also requires certain expanded disclosures for discontinued operations and disclosure of the pre-tax profit or loss of an individually significant component of an entity that does not qualify for discontinued operations reporting. The adoption of this ASU did not have a material effect on Ambac's financial statements. Issued: In April 2015, the FASB issued ASU 2015-03, Interest - Imputation of Interest (Subtopic 835-30) . This ASU simplifies the presentation of debt issuance costs by requiring that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs are not affected by the amendments in this ASU. The ASU is effective for annual periods and interim periods within those annual periods beginning after December 15, 2015. Early adoption is also permitted for financial statements that have not been previously issued. Upon adoption, the ASU must be retrospectively applied to all prior periods presented. Ambac has not determined whether it will adopt ASU 2015-03 prior to January 1, 2016. The adoption of this ASU is not expected to have a material impact on Ambac's financial statements. In May 2015, the FASB issued ASU 2015-07, Fair Value Measurement (Topic 820) - Disclosures for Investments in Certain Entities That Calculate Net Asset Value per Share (or Its Equivalent) . Reporting entities are permitted to use net asset value ("NAV") as a practical expedient to measure the fair value of certain investments. Under current U.S. GAAP, investments that use the NAV practical expedient to measure fair value are categorized within the fair value hierarchy as level 2 or level 3 investments depending on their redemption attributes, which has led to diversity in practice. This ASU will remove the requirement to categorize within the fair value hierarchy all investments that use the NAV practical expedient for fair value measurement purposes. Furthermore, the ASU will remove the requirement to make certain disclosures for all investments that are eligible to be measured at fair value using the NAV practical expedient. The ASU is effective for fiscal years beginning after December 15, 2015 and interim periods with those fiscal years. The ASU must be applied retrospectively to all prior periods presented. Ambac will adopt ASU 2015-07 on January 1, 2016. The adoption of this ASU is not expected to have a material impact on Ambac's financial statements. In May 2015, the FASB issued ASC 2015-09, Financial Services - Insurance (Topic 944) - Disclosures about Short-Duration Contracts. The primary objective of this ASU is to improve disclosures for insurance entities which issue short-duration contracts. The ASU made significant amendments to the Short-Duration Contract disclosure section and limited amendments affecting the General disclosure section of Topic 944. Ambac, as a provider of financial guarantee contracts, is subject to the General sections but not the Short-Duration Contract sections of Topic 944. The limited amendments made to the General disclosure section are not expected to have a material impact on Ambac's financial statement disclosures. The ASU is effective for annual periods beginning after December 15, 2015, and interim periods within annual periods beginning after December 15, 2016. Ambac will adopt ASU 2015-09 on December 31, 2016.

Basis of Presentation and Sig21

Basis of Presentation and Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2015
Goodwill [Line Items]
Summary of Activity in Goodwill for Financial Guarantee Reporting Unit	The following is a summary of activity in goodwill for the Financial Guarantee reporting unit: Nine Months Ended September 30, 2015 Year Ended December 31, 2014 Beginning balance $ 514,511 $ 514,511 Impairment loss (514,511 ) — Ending balance $ — $ 514,511

Special Purpose Entities, Inc22

Special Purpose Entities, Including Variable Interest Entities (Tables)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Summary of Fair Value of Fixed Income Securities, by Asset-Type, Held by Consolidated Variable Interest Entities	The table below provides the fair value of fixed income securities, by asset-type, held by consolidated VIEs as of September 30, 2015 and December 31, 2014 : September 30, December 31, Investments: Corporate obligations $ 2,679,895 $ 2,743,050 Total variable interest entity assets: fixed income securities $ 2,679,895 $ 2,743,050
Supplemental Information about Loans Held as Assets and Long-Term Debt Associated with Consolidated Variable Interest Entities	The following table provides supplemental information about the loans held as assets and long-term debt associated with the VIEs for which the fair value option has been elected as of September 30, 2015 and December 31, 2014 : Estimated fair value Unpaid principal balance September 30, 2015 Loans $ 12,183,061 $ 9,446,235 Long-term debt 12,791,012 11,366,061 December 31, 2014 Loans 12,371,177 10,236,695 Long-term debt $ 12,882,076 $ 11,925,499
Summary of Carrying Amount of Assets, Liabilities and Maximum Exposure to Loss of Ambac's Variable Interests in Non-Consolidated Variable Interest Entities	The following table displays the carrying amount of the assets, liabilities and maximum exposure to loss of Ambac’s variable interests in non-consolidated VIEs resulting from financial guarantee and derivative contracts by major underlying asset classes, as of September 30, 2015 and December 31, 2014 : Carrying Value of Assets and Liabilities Maximum (1) Insurance (2) Insurance (3) Net Derivative (4) September 30, 2015: Global structured finance: Collateralized debt obligations $ 1,041,843 $ 271 $ 3,716 $ (139,859 ) Mortgage-backed—residential 17,722,719 1,034,921 2,740,222 — Other consumer asset-backed 4,321,282 51,802 648,958 (349 ) Other commercial asset-backed 2,597,067 115,751 105,826 — Other 3,308,329 82,160 484,964 16,006 Total global structured finance 28,991,240 1,284,905 3,983,686 (124,202 ) Global public finance 30,463,734 427,717 483,506 (21,421 ) Total $ 59,454,974 $ 1,712,622 $ 4,467,192 $ (145,623 ) December 31, 2014: Global structured finance: Collateralized debt obligations $ 1,386,100 $ 345 $ 4,000 $ (145,565 ) Mortgage-backed—residential 19,464,549 1,011,888 2,924,987 — Other consumer asset-backed 5,109,776 65,204 885,572 (36,877 ) Other commercial asset-backed 3,119,891 135,215 128,988 — Other 3,801,382 97,345 599,915 18,176 Total global structured finance 32,881,698 1,309,997 4,543,462 (164,266 ) Global public finance 31,639,004 457,774 533,192 (22,135 ) Total $ 64,520,702 $ 1,767,771 $ 5,076,654 $ (186,401 ) (1) Maximum exposure to loss represents the maximum future payments of principal and interest on insured obligations and derivative contracts plus Deferred Amounts and accrued and unpaid interest thereon. Ambac’s maximum exposure to loss does not include the benefit of any financial instruments (such as reinsurance or hedge contracts) that Ambac may utilize to mitigate the risks associated with these variable interests. (2) Insurance assets represent the amount recorded in “Premium receivables” and “Subrogation recoverable” for financial guarantee contracts on Ambac’s Consolidated Balance Sheets. (3) Insurance liabilities represent the amount recorded in “Loss and loss expense reserves” and “Unearned premiums” for financial guarantee contracts on Ambac’s Consolidated Balance Sheets. (4) Net derivative assets (liabilities) represent the fair value recognized on credit derivative contracts and interest rate swaps on Ambac’s Consolidated Balance Sheets.

Comprehensive Income (Tables)

Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2015
Equity [Abstract]
Schedule of Changes in Balances of Each Component of Accumulated Other Comprehensive Income	The following tables detail the changes in the balances of each component of accumulated other comprehensive income for the affected periods: Unrealized Gains (1) Amortization of (1) Gain (Loss) on (1) Total Three Months Ended September 30, 2015 Beginning Balance $ 79,406 $ 9,784 $ 6,172 $ 95,362 Other comprehensive income before reclassifications 1,342 — (30,637 ) (29,295 ) Amounts reclassified from accumulated other comprehensive income 7,040 (220 ) — 6,820 Net current period other comprehensive income (loss) 8,382 (220 ) (30,637 ) (22,475 ) Balance at September 30, 2015 $ 87,788 $ 9,564 $ (24,465 ) $ 72,887 Three Months Ended September 30, 2014 Beginning Balance $ 231,975 $ 10,439 $ 63,914 $ 306,328 Other comprehensive income before reclassifications (12,222 ) — (38,034 ) (50,256 ) Amounts reclassified from accumulated other comprehensive income (5,003 ) (204 ) — (5,207 ) Net current period other comprehensive income (loss) (17,225 ) (204 ) (38,034 ) (55,463 ) Balance at September 30, 2014 $ 214,750 $ 10,235 $ 25,880 $ 250,865 (1) All amounts are net of tax and noncontrolling interest. Amounts in parentheses indicate debits. Unrealized Gains (1) Amortization of (1) Gain (Loss) on (1) Total Nine Months Ended September 30, 2015: Beginning Balance $ 210,693 $ 10,031 $ (441 ) $ 220,283 Other comprehensive income before reclassifications (85,313 ) — (24,024 ) (109,337 ) Amounts reclassified from accumulated other comprehensive income (37,592 ) (467 ) — (38,059 ) Net current period other comprehensive income (loss) (122,905 ) (467 ) (24,024 ) (147,396 ) Balance at September 30, 2015 $ 87,788 $ 9,564 $ (24,465 ) $ 72,887 Nine Months Ended September 30, 2014: Beginning Balance $ (41,910 ) $ 10,847 $ 42,724 $ 11,661 Other comprehensive income before reclassifications 261,879 — (16,844 ) 245,035 Amounts reclassified from accumulated other comprehensive income (5,219 ) (612 ) — (5,831 ) Net current period other comprehensive income (loss) 256,660 (612 ) (16,844 ) 239,204 Balance at September 30, 2014 $ 214,750 $ 10,235 $ 25,880 $ 250,865 (1) All amounts are net of tax and noncontrolling interest. Amounts in parentheses indicate debits.
Schedule of Amounts Reclassed Out of Each Component of Accumulated Other Comprehensive Income	The following table details the significant amounts reclassified from each component of accumulated other comprehensive income for the affected periods: Amount Reclassified from Accumulated (1) Affected Line Item in the Details about Accumulated Other Three Months Ended September 30, Consolidated Statement of Comprehensive Income Components 2015 2014 Total Comprehensive Income Unrealized Gains (Losses) on Available-for-Sale Securities $ 7,040 $ (5,003 ) Net realized investment (losses) gains — — Tax (expense) benefit $ 7,040 $ (5,003 ) Net of tax and noncontrolling interest (3) Amortization of Postretirement Benefit Prior service cost $ (167 ) $ (166 ) Underwriting and operating expenses (2) Actuarial gains (losses) (53 ) (38 ) Underwriting and operating expenses (2) (220 ) (204 ) Total before tax — — Tax (expense) benefit $ (220 ) $ (204 ) Net of tax and noncontrolling interest (3) Total reclassifications for the period $ 6,820 $ (5,207 ) Net of tax and noncontrolling interest (3) (1) Amounts in parentheses indicate debits to the Consolidated Statement of Total Comprehensive Income. (2) These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. (3) Amount agrees w ith amount reported as reclassifications from AOCI in the disclosure about changes in AOCI balances. Amount Reclassified from Accumulated (1) Affected Line Item in the Details about Accumulated Other Nine Months Ended September 30, Consolidated Statement of Comprehensive Income Components 2015 2014 Total Comprehensive Income Unrealized Gains (Losses) on Available-for-Sale Securities $ (37,592 ) $ (5,219 ) Net realized investment gains — — Tax (expense) benefit $ (37,592 ) $ (5,219 ) Net of tax and noncontrolling interest (3) Amortization of Postretirement Benefit Prior service cost $ (500 ) $ (498 ) Underwriting and operating expenses (2) Actuarial gains (losses) 33 (114 ) Underwriting and operating expenses (2) (467 ) (612 ) Total before tax — — Tax (expense) benefit $ (467 ) $ (612 ) Net of tax and noncontrolling interest (3) Total reclassifications for the period $ (38,059 ) $ (5,831 ) Net of tax and noncontrolling interest (3) (1) Amounts in parentheses indicate debits to the Consolidated Statement of Total Comprehensive Income. (2) These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. (3) Amount agrees w ith amount reported as reclassifications from AOCI in the disclosure about changes in AOCI balances.

Net Income Per Share (Tables)

Net Income Per Share (Tables)	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Reconciliation of Common Shares Used for Basic and Diluted Earnings Per Share	The following table provides a reconciliation of the common shares used for basic net income per share to the diluted shares used for diluted net income per share: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Basic weighted average shares outstanding 45,174,521 45,115,882 45,173,671 45,083,831 Effect of potential dilutive shares: Warrants — 1,469,203 1,154,313 1,892,211 Stock options — 8,220 7,083 10,569 Restricted stock units — 31,384 14,418 40,473 Performance stock units — — 2,729 — Diluted weighted average shares outstanding 45,174,521 46,624,689 46,352,214 47,027,084

Financial Guarantee Insurance25

Financial Guarantee Insurance Contracts (Tables)	9 Months Ended
	Sep. 30, 2015
Insurance [Line Items]
Schedule of Loss And Loss Expense Reserves And Subrogation Recoverable Table [Table Text Block]	Below are the components of the Loss and loss expense reserves liability and the Subrogation recoverable asset at September 30, 2015 and December 31, 2014 : Unpaid Claims Present Value of Expected Balance Sheet Line Item Claims Accrued Claims and Recoveries Unearned Gross Loss and September 30, 2015: Loss and loss expense reserves $ 2,193,214 $ 324,125 $ 3,137,857 $ (1,238,561 ) $ (179,120 ) $ 4,237,515 Subrogation recoverable 785,993 125,225 148,147 (2,041,567 ) — (982,202 ) Totals $ 2,979,207 $ 449,350 $ 3,286,004 $ (3,280,128 ) $ (179,120 ) $ 3,255,313 December 31, 2014: Loss and loss expense reserves $ 2,172,041 $ 234,802 $ 3,792,133 $ (1,205,621 ) $ (241,348 ) $ 4,752,007 Subrogation recoverable 772,948 94,425 197,751 (2,018,398 ) — (953,274 ) Totals $ 2,944,989 $ 329,227 $ 3,989,884 $ (3,224,019 ) $ (241,348 ) $ 3,798,733
Summary of Gross Premium Receivable Roll-Forward (Direct and Assumed Contracts)	Below is the gross premium receivable roll-forward (direct and assumed contracts) for the affected periods: Nine Months Ended September 30, 2015 2014 Beginning premium receivable $ 1,000,607 $ 1,453,021 Premium receipts (70,940 ) (100,646 ) Adjustments for changes in expected and contractual cash flows (39,613 ) (93,795 ) Accretion of premium receivable discount 18,795 29,644 Changes to uncollectable premiums 1,978 (801 ) Other adjustments (including foreign exchange) (15,381 ) (20,791 ) Ending premium receivable $ 895,446 $ 1,266,632
Effect of Reinsurance on Premiums Written and Earned	The effect of reinsurance on premiums written and earned for the respective periods was as follows: Three Months Ended September 30, 2015 Three Months Ended September 30, 2014 Written Earned Written Earned Direct $ (8,710 ) $ 77,982 $ (13,700 ) $ 68,685 Assumed — 22 — 23 Ceded (105 ) 6,469 (2,805 ) 3,877 Net premiums $ (8,605 ) $ 71,535 $ (10,895 ) $ 64,831 Nine Months Ended September 30, 2015 Nine Months Ended September 30, 2014 Written Earned Written Earned Direct $ (18,840 ) $ 214,787 $ (64,952 ) $ 222,894 Assumed — 66 — 114 Ceded (882 ) 16,721 (7,316 ) 10,617 Net premiums $ (17,958 ) $ 198,132 $ (57,636 ) $ 212,391
Summarized Future Gross Undiscounted Premiums Expected to be Collected and Future Expected Premiums Earned, Net of Reinsurance	The table below summarizes the future gross undiscounted premiums to be collected and future premiums earned, net of reinsurance at September 30, 2015 : Future premiums (1) Future (1) Three months ended: December 31, 2015 $ 21,054 $ 36,341 Twelve months ended: December 31, 2016 82,229 125,182 December 31, 2017 76,613 105,390 December 31, 2018 71,514 94,004 December 31, 2019 67,678 87,387 Five years ended: December 31, 2024 298,847 359,221 December 31, 2029 248,187 255,225 December 31, 2034 174,358 160,285 December 31, 2039 63,810 65,206 December 31, 2044 23,749 22,408 December 31, 2049 9,518 9,722 December 31, 2054 1,244 2,183 December 31, 2059 5 3 Total $ 1,138,806 $ 1,322,557 (1) Future premiums to be collected is undiscounted which are used to derive the discounted premium receivable asset recorded on Ambac's balance sheet. Future premiums to be earned, net of reinsurance relate to the unearned premium liability and deferred ceded premium asset recorded on Ambac’s balance sheet. The use of contractual lives for many bond types which do not have homogeneous pools of underlying collateral is required in the calculation of the premium receivable, as further described in Note 2. Basis of Presentation and Significant Accounting Principles in the Notes to Consolidated Financial Statements included in Ambac's Annual Report on Form 10-K for the year ended December 31, 2014 . This results in a different premium receivable balance than if expected lives were considered. If installment paying policies are retired or prepay early, premiums reflected in the premium receivable asset and amounts reported in the above table for such policies may not be collected. Future premiums to be earned also considers the use of contractual lives for many bond types which do not have homogeneous pools of underlying collateral, which results in higher unearned premium than if expected lives were considered. If those bonds types are retired early, premium earnings may be negative in the period of call or refinancing.
Summary of Loss Reserve Roll-Forward, Net of Subrogation Recoverable and Reinsurance	Below is the loss and loss expense reserve roll-forward, net of subrogation recoverable and reinsurance, for the affected periods: Nine Months Ended September 30, 2015 2014 Beginning gross loss and loss expense reserves $ 3,798,733 $ 5,470,234 Less reinsurance on loss and loss expense reserves 100,355 122,357 Beginning balance of net loss and loss expense reserves $ 3,698,378 $ 5,347,877 Changes in the loss and loss expense reserves due to: Current year: Establishment of new loss and loss expense reserves, gross of RMBS subrogation and net of reinsurance 1,404 236 Claim and loss expense (payments) recoveries, net of subrogation and reinsurance — (4 ) Total current year 1,404 232 Prior years: Change in previously established loss and loss expense reserves, gross of RMBS subrogation and net of reinsurance (414,642 ) (934 ) Claim and loss expense (payments) recoveries, net of subrogation and reinsurance (61,740 ) 67,736 (Increase) decrease in previously established RMBS subrogation recoveries, net of reinsurance (31,744 ) (6,315 ) Total prior years (508,126 ) 60,487 Net change in net loss and loss expense reserves (506,722 ) 60,719 Ending net loss and loss expense reserves 3,191,656 5,408,596 Add reinsurance on loss and loss expense reserves (1) 63,657 105,641 Ending gross loss and loss expense reserves $ 3,255,313 $ 5,514,237 (1) Reinsurance recoverable reported on the Balance Sheet also includes reinsurance recoverables (payables) of previously presented loss and loss expenses of $4,662 and $(130) as of September 30, 2015 and 2014 , respectively.
Summary of Information Related to Policies Currently Included in Ambac's Loss Reserves or Subrogation Recoverable	The tables below summarize information related to policies currently included in Ambac’s loss and loss expense reserves or subrogation recoverable at September 30, 2015 and December 31, 2014 . Gross par exposures include capital appreciation bonds which are reported at the par amount at the time of issuance of the insurance policy. The weighted average risk-free rate used to discount loss reserves at September 30, 2015 and December 31, 2014 was 2.3% and 2.3% , respectively. Surveillance Categories as of September 30, 2015 I/SL IA II III IV V Total Number of policies 44 17 30 65 164 3 323 Remaining weighted-average contract period (in years) 7 17 14 19 14 6 16 Gross insured contractual payments outstanding: Principal $ 2,099,540 $ 305,681 $ 1,338,428 $ 3,913,273 $ 8,897,699 $ 54,590 $ 16,609,211 Interest 730,755 138,831 356,410 2,940,877 1,827,031 18,157 6,012,061 Total $ 2,830,295 $ 444,512 $ 1,694,838 $ 6,854,150 $ 10,724,730 $ 72,747 $ 22,621,272 Gross undiscounted claim liability (1) $ 15,820 $ 6,036 $ 46,817 $ 1,639,016 $ 6,076,327 $ 72,747 $ 7,856,763 Discount, gross claim liability (786 ) (596 ) (12,179 ) (524,462 ) (697,119 ) (6,146 ) (1,241,288 ) Gross claim liability before all subrogation and before reinsurance $ 15,034 $ 5,440 $ 34,638 $ 1,114,554 $ 5,379,208 $ 66,601 $ 6,615,475 Less: Gross RMBS subrogation (2) — — — — (2,569,094 ) — (2,569,094 ) Discount, RMBS subrogation — — — — 13,633 — 13,633 Discounted RMBS subrogation, before reinsurance — — — — (2,555,461 ) — (2,555,461 ) Less: Gross other subrogation (3) — — (12,719 ) (133,640 ) (641,812 ) (13,219 ) (801,390 ) Discount, other subrogation — — 3,538 35,910 33,468 3,807 76,723 Discounted other subrogation, before reinsurance — — (9,181 ) (97,730 ) (608,344 ) (9,412 ) (724,667 ) Gross claim liability, net of all subrogation and discounts, before reinsurance $ 15,034 $ 5,440 $ 25,457 $ 1,016,824 $ 2,215,403 $ 57,189 $ 3,335,347 Less: Unearned premium revenue (10,207 ) (2,089 ) (17,961 ) (86,842 ) (61,546 ) (475 ) (179,120 ) Plus: Loss expense reserves — 80 819 18,708 79,479 — 99,086 Gross loss and loss expense reserves $ 4,827 $ 3,431 $ 8,315 $ 948,690 $ 2,233,336 $ 56,714 $ 3,255,313 Reinsurance recoverable reported on Balance Sheet (4) $ 641 $ 895 $ 67 $ 82,496 $ (15,780 ) $ — $ 68,319 (1) Gross undiscounted claim liability includes unpaid claims, including accrued interest on Deferred Amounts, on policies allocated to the Segregated Account and Ambac's estimate of expected future claims. (2) RMBS subrogation represents Ambac’s probability-weighted estimate of subrogation recoveries from RMBS transaction sponsors for representation and warranty ("R&W") breaches. (3) Other subrogation primarily represents subrogation related to excess spread or other contractual cash flows on public finance and structured finance transactions, including RMBS. (4) Reinsurance recoverable reported on Balance Sheet includes reinsurance recoverables of $63,657 related to future loss and loss expenses and $4,662 related to presented loss and loss expenses. Surveillance Categories as of December 31, 2014 I/SL IA II III IV V Total Number of policies 36 26 33 69 160 1 325 Remaining weighted-average contract period (in years) 8 12 15 21 12 6 16 Gross insured contractual payments outstanding: Principal $ 1,026,513 $ 519,291 $ 3,091,744 $ 3,792,559 $ 9,892,760 $ 47 $ 18,322,914 Interest 418,746 212,296 1,878,770 2,765,537 1,979,627 19 7,254,995 Total $ 1,445,259 $ 731,587 $ 4,970,514 $ 6,558,096 $ 11,872,387 $ 66 $ 25,577,909 Gross undiscounted claim liability (1) $ 16,360 $ 11,525 $ 155,488 $ 2,040,402 $ 6,456,139 $ 60 $ 8,679,974 Discount, gross claim liability (1,147 ) (937 ) (16,438 ) (716,812 ) (774,611 ) (3 ) (1,509,948 ) Gross claim liability before all subrogation and before reinsurance $ 15,213 $ 10,588 $ 139,050 $ 1,323,590 $ 5,681,528 $ 57 $ 7,170,026 Less: Gross RMBS subrogation (2) — — — — (2,541,219 ) — (2,541,219 ) Discount, RMBS subrogation — — — — 17,679 — 17,679 Discounted RMBS subrogation, before reinsurance — — — — (2,523,540 ) — (2,523,540 ) Less: Gross other subrogation (3) — — (18,034 ) (127,143 ) (647,110 ) — (792,287 ) Discount, other subrogation — — 6,069 36,779 48,960 — 91,808 Discounted other subrogation, before reinsurance — — (11,965 ) (90,364 ) (598,150 ) — (700,479 ) Gross claim liability, net of all subrogation and discounts, before reinsurance $ 15,213 $ 10,588 $ 127,085 $ 1,233,226 $ 2,559,838 $ 57 $ 3,946,007 Less: Unearned premium revenue (10,945 ) (3,432 ) (73,749 ) (88,332 ) (64,890 ) — (241,348 ) Plus: Loss expense reserves 3 1,303 1,968 6,470 84,330 — 94,074 Gross loss and loss expense reserves $ 4,271 $ 8,459 $ 55,304 $ 1,151,364 $ 2,579,278 $ 57 $ 3,798,733 Reinsurance recoverable reported on Balance Sheet (4) $ 73 $ 890 $ 1,355 $ 110,957 $ (13,437 ) $ — $ 99,838 (1) Gross undiscounted claim liability includes unpaid claims, including accrued interest on Deferred Amounts, on policies allocated to the Segregated Account and Ambac's estimate of expected future claims. (2) RMBS subrogation represents Ambac’s probability-weighted estimate of subrogation recoveries from RMBS transaction sponsors for R&W breaches. (3) Other subrogation primarily represents subrogation related to excess spread or other contractual cash flows on public finance and structured finance transactions, including RMBS. (4) Reinsurance recoverable reported on Balance Sheet includes reinsurance recoverables of $100,355 related to future loss and loss expenses and $(517) related to presented loss and loss expenses.
Summary of Balance of Subrogation Recoveries and Related Claim Liabilities, by Estimation Approach	The balance of RMBS subrogation recoveries and the related loss reserves, using random samples as the estimation approach, at September 30, 2015 and December 31, 2014 , are as follows: Random Samples Approach Gross loss (1) Subrogation (2)(3) Gross loss At September 30, 2015 $ 1,856,754 $ (2,555,461 ) $ (698,707 ) At December 31, 2014 $ 1,897,426 $ (2,523,540 ) $ (626,114 ) (1) Includes unpaid RMBS claims, including accrued interest on Deferred Amounts, on policies allocated to the Segregated Account. (2) The amount of recorded subrogation recoveries related to each securitization is limited to ever-to-date paid and unpaid losses plus the present value of expected cash flows for each policy. To the extent losses have been paid but not yet fully recovered, the recorded amount of RMBS subrogation recoveries may exceed the sum of the unpaid claims and the present value of expected cash flows for a given policy. The net cash inflow for these policies is recorded as a “Subrogation recoverable” asset. For those transactions where the subrogation recovery is less than the sum of unpaid claims and the present value of expected cash flows, the net cash outflow for these policies is recorded as a “Loss and loss expense reserves” liability. (3) The sponsor’s repurchase obligation may differ depending on the terms of the particular transaction and the status of the specific loan, such as whether it is performing or has been liquidated or charged off. The estimated subrogation recovery for these transactions is based primarily on loan level data provided through trustee reports received in the normal course of our surveillance activities or provided by the sponsor. While this data may not include all the components of the sponsor’s contractual repurchase obligation we believe it is the best information available to estimate the subrogation recovery.
Summary of Rollforward of RMBS Subrogation, by Estimation Approach	Below is the rollforward of RMBS subrogation, by estimation approach, for the affected periods: Random Adverse Total Discounted RMBS subrogation (gross of reinsurance) at January 1, 2015 $ 2,523,540 $ — $ 2,523,540 Changes recognized in 2015: Impact of sponsor actions (2) — — — All other changes (3) 31,921 — 31,921 Discounted RMBS subrogation (gross of reinsurance) at September 30, 2015 $ 2,555,461 $ — $ 2,555,461 Discounted RMBS subrogation (gross of reinsurance) at January 1, 2014 $ 953,825 $ 1,252,773 $ 2,206,598 Changes recognized in 2014: Additional transactions reviewed 24,565 — 24,565 Changes in estimation approach (1) 1,272,532 (1,218,681 ) 53,851 Impact of sponsor actions (2) (90,000 ) — (90,000 ) All other changes (3) 53,508 (34,092 ) 19,416 Discounted RMBS subrogation (gross of reinsurance) at September 30, 2014 $ 2,214,430 $ — $ 2,214,430 (1) Represents estimated subrogation for those transactions previously evaluated using the Adverse sample approach, which are evaluated using a Random Sample approach beginning June 30, 2014. The amounts shown in the Random and Adverse Sample columns are different as a result of the differences in estimation approaches. (2) Sponsor actions include loan repurchases, direct payments to Ambac and other contributions. (3) All other changes which may impact RMBS subrogation recoveries include changes in actual or projected collateral performance, changes in the creditworthiness of a sponsor, and/or the projected timing of recoveries. All other changes may also include estimates of potential sponsor settlements that are currently in negotiation but have not been subject to a sampling approach. However, such estimates are not material to Ambac’s financial results and therefore are included in the Random Sample column of this table.
Insurance Intangible Asset [Member]
Insurance [Line Items]
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	The estimated future amortization expense for the net insurance intangible asset is as follows: 2015 2016 2017 2018 2019 Thereafter Amortization expense $ 29,892 $ 110,315 $ 97,714 $ 89,267 $ 82,506 $ 869,754

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Summary of Carrying Amount and Fair Value of Ambac's Financial Assets and Liabilities	The following table sets forth the carrying amount and fair value of Ambac’s financial assets and liabilities as of September 30, 2015 and December 31, 2014 , including the level within the fair value hierarchy at which fair value measurements are categorized. As required by the Fair Value Measurement Topic of the ASC financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Carrying Total Fair Fair Value Measurements Categorized as: Level 1 Level 2 Level 3 September 30, 2015: Financial assets: Fixed income securities: Municipal obligations $ 419,001 $ 419,001 $ — $ 419,001 $ — Corporate obligations 1,587,578 1,587,578 — 1,587,578 — Foreign obligations 103,654 103,654 — 103,654 — U.S. government obligations 30,863 30,863 30,863 — — U.S. agency obligations 4,281 4,281 — 4,281 — Residential mortgage-backed securities 1,871,483 1,871,483 — 1,487,694 383,789 Collateralized debt obligations 81,912 81,912 — 81,912 — Other asset-backed securities 858,104 858,104 — 858,104 — Fixed income securities, pledged as collateral: U.S. government obligations 64,972 64,972 64,972 — — Short term investments 364,780 364,780 305,950 58,830 — Other investments 314,934 302,791 — 290,723 12,068 Cash and cash equivalents 27,099 27,099 27,099 — — Loans 5,499 5,479 — — 5,479 Derivative assets: Credit derivatives 1,345 1,345 — — 1,345 Interest rate swaps—asset position 89,743 89,743 — 23,796 65,947 Interest rate swaps—liability position — — — — — Futures contracts — — — — — Other assets 9,322 9,322 — — 9,322 Variable interest entity assets: Fixed income securities: Corporate obligations 2,679,895 2,679,895 — — 2,679,895 Restricted cash 5,895 5,895 5,895 — — Loans 12,183,061 12,183,061 — — 12,183,061 Total financial assets $ 20,703,421 $ 20,691,258 $ 434,779 $ 4,915,573 $ 15,340,906 Financial liabilities: Obligations under investment agreements $ 100,358 $ 100,858 $ — $ — $ 100,858 Long term debt, including accrued interest 1,457,996 1,318,300 — 139,002 1,179,298 Derivative liabilities: Credit derivatives 31,232 31,232 — — 31,232 Interest rate swaps—asset position (63,785 ) (63,785 ) — (63,785 ) — Interest rate swaps—liability position 408,168 408,168 — 270,049 138,119 Futures contracts 220 220 220 — — Liabilities for net financial guarantees written (1) 2,414,692 3,044,698 — — 3,044,698 Variable interest entity liabilities: Long-term debt 12,791,012 12,791,012 — 10,647,480 2,143,532 Derivative liabilities: Interest rate swaps—liability position 2,065,224 2,065,224 — 2,065,224 — Currency swaps—asset position (31,429 ) (31,429 ) — (31,429 ) — Total financial liabilities $ 19,173,688 $ 19,664,498 $ 220 $ 13,026,541 $ 6,637,737 (1) The carrying value of net financial guarantees written includes the following balance sheet items: Premium receivables; Reinsurance recoverable on paid and unpaid losses; Deferred ceded premium; Subrogation recoverable; Insurance intangible asset; Unearned premiums; Loss and loss expense reserves; Ceded premiums payable, premiums taxes payable and other deferred fees recorded in Other liabilities. Carrying Total Fair Fair Value Measurements Categorized as: Level 1 Level 2 Level 3 December 31, 2014: Financial assets: Fixed income securities: Municipal obligations $ 525,792 $ 525,792 $ — $ 525,792 $ — Corporate obligations 1,385,594 1,385,594 — 1,381,786 3,808 Foreign obligations 127,757 127,757 — 127,757 — U.S. government obligations 42,979 42,979 42,979 — — U.S. agency obligations 29,486 29,486 — 29,486 — Residential mortgage-backed securities 1,710,955 1,710,955 — 1,516,562 194,393 Collateralized debt obligations 21,122 21,122 — 21,122 — Other asset-backed securities 882,001 882,001 — 882,001 — Fixed income securities, pledged as collateral: U.S. government obligations 64,267 64,267 64,267 — — Short term investments 360,065 360,065 358,190 1,875 — Other investments 357,016 349,468 — 336,013 13,455 Cash and cash equivalents 73,903 73,903 73,903 — — Loans 5,714 5,634 — — 5,634 Derivative assets: Credit derivatives 2,043 2,043 — — 2,043 Interest rate swaps—asset position 106,974 106,974 — 106,974 — Interest rate swaps—liability position — — — — — Futures contracts — — — — — Other assets 12,036 12,036 — — 12,036 Variable interest entity assets: Fixed income securities: Corporate obligations 2,743,050 2,743,050 — — 2,743,050 Restricted cash 7,708 7,708 7,708 — — Loans 12,371,177 12,371,177 — — 12,371,177 Total financial assets $ 20,829,639 $ 20,822,011 $ 547,047 $ 4,929,368 $ 15,345,596 Financial liabilities: Obligations under investment agreements $ 160,079 $ 161,821 $ — $ — $ 161,821 Long term debt, including accrued interest 1,273,805 1,379,864 — — 1,379,864 Derivative liabilities: Credit derivatives 75,502 75,502 — — 75,502 Interest rate swaps—asset position (54,666 ) (54,666 ) — (54,666 ) — Interest rate swaps—liability position 385,546 385,546 — 243,659 141,887 Futures contracts 562 562 562 — — Other contracts — — — — — Liabilities for net financial guarantees written (1) 2,923,652 4,539,000 — — 4,539,000 Variable interest entity liabilities: Long-term debt 12,882,076 12,882,076 — 11,618,412 1,263,664 Derivative liabilities: Interest rate swaps—liability position 2,133,268 2,133,268 — 2,133,268 — Currency swaps—liability position 66,895 66,895 — 66,895 — Total financial liabilities $ 19,846,719 $ 21,569,868 $ 562 $ 14,007,568 $ 7,561,738 (1) The carrying value of net financial guarantees written includes the following balance sheet items: Premium receivables; Reinsurance recoverable on paid and unpaid losses; Deferred ceded premium; Subrogation recoverable; Insurance intangible asset; Unearned premiums; Loss and loss expense reserves; Ceded premiums payable, premiums taxes payable and other deferred fees recorded in Other liabilities.
Information about Valuation Inputs for Variable Interest Entity Assets and Liabilities Classified as Level 3	Information about the above described model inputs used to determine the fair value of each class of credit derivatives, including the CVA as a percentage of the gross mark-to-market liability before considering Ambac credit risk (“CVA percentage”), as of September 30, 2015 and December 31, 2014 is summarized below: CLOs Other (1) September 30, 2015: Notional outstanding $ 341,668 $ 913,647 Weighted average reference obligation price 98.5 85.9 Weighted average life (WAL) in years 1.0 4.2 Weighted average credit rating AA BBB- Weighted average relative change ratio 36.3 % 45.3 % CVA percentage 7.48 % 22.91 % Fair value of derivative liabilities $ 1,740 $ 28,125 December 31, 2014: Notional outstanding $ 549,923 $ 921,036 Weighted average reference obligation price 98.9 86.8 Weighted average life (WAL) in years 1.8 5.7 Weighted average credit rating AA BBB- Weighted average relative change ratio 35.9 % 49.0 % CVA percentage 5.40 % 15.82 % Fair value of derivative liabilities $ 2,027 $ 71,104 (1) Excludes contracts for which fair values are based on credit derivative quotes rather than reference obligation quotes. Such contracts have a combined notional outstanding of $58,482 , WAL of 0.4 and liability fair value of $22 as of September 30, 2015 . Other inputs to the valuation of these transactions at September 30, 2015 include weighted average quotes of less than 1% of notional, weighted average rating of A+ and Ambac CVA percentage of 1.09% . As of December 31, 2014 , these contracts had a combined notional outstanding of $58,800 , WAL of 1.2 years and liability fair value of $328 . Other inputs to the valuation of these transactions at December 31, 2014 include weighted average quotes of 1% of notional, weighted average rating of A and Ambac CVA percentage of 2.21% .
Summary of Changes in Level 3 Fair Value Category	The following tables present the changes in the Level 3 fair value category for the periods presented in 2015 and 2014 . Ambac classifies financial instruments in Level 3 of the fair value hierarchy when there is reliance on at least one significant unobservable input to the valuation model. In addition to these unobservable inputs, the valuation models for Level 3 financial instruments typically also rely on a number of inputs that are readily observable either directly or indirectly. Thus, the gains and losses presented below include changes in the fair value related to both observable and unobservable inputs. Level 3 - Financial Assets and Liabilities Accounted for at Fair Value VIE Assets and Liabilities Investments Other Derivatives Investments Loans Long-term Total Three Months Ended September 30, 2015: Balance, beginning of period $ 380,332 $ 9,704 $ (119,309 ) $ 2,747,181 $ 13,005,216 $ (2,166,826 ) $ 13,856,298 Total gains/(losses) realized and unrealized: Included in earnings 8,429 (382 ) 20,073 39,630 44,404 (59,760 ) 52,394 Included in other comprehensive income (4,288 ) — — (106,916 ) (471,321 ) 79,314 (503,211 ) Purchases 28 — — — — — 28 Issuances — — — — — — — Sales — — — — — — — Settlements (712 ) — (2,822 ) — (70,115 ) 3,740 (69,909 ) Transfers into Level 3 — — — — — — — Transfers out of Level 3 — — — — — — — Deconsolidation of VIEs — — — — (325,123 ) — (325,123 ) Balance, end of period $ 383,789 $ 9,322 $ (102,058 ) $ 2,679,895 $ 12,183,061 $ (2,143,532 ) $ 13,010,477 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ — $ (382 ) $ (12,285 ) $ 39,630 $ 102,901 $ (107,567 ) $ 22,297 Three Months Ended September 30, 2014: Balance, beginning of period $ 66,352 $ 12,782 $ (218,661 ) $ 2,688,388 $ 13,743,231 $ (1,375,049 ) $ 14,917,043 Total gains/(losses) realized and unrealized: Included in earnings 835 (381 ) 3,885 105,116 209,028 (16,961 ) 301,522 Included in other comprehensive income (254 ) — — (141,821 ) (678,944 ) 62,314 (758,705 ) Purchases — — — — — — — Issuances — — — — — — — Sales (3,388 ) — — — — — (3,388 ) Settlements (885 ) — (1,126 ) — (73,042 ) 4,102 (70,951 ) Transfers into Level 3 — — — — — — — Transfers out of Level 3 — — — — (696,789 ) 36,891 (659,898 ) Balance, end of period $ 62,660 $ 12,401 $ (215,902 ) $ 2,651,683 $ 12,503,484 $ (1,288,703 ) $ 13,725,623 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ — $ (381 ) $ 3,229 $ 105,116 $ 215,296 $ (16,047 ) $ 307,213 Level 3 - Financial Assets and Liabilities Accounted for at Fair Value VIE Assets and Liabilities Investments Other Derivatives Investments Loans Long-term Total Nine Months Ended September 30, 2015: Balance, beginning of period $ 198,201 $ 12,036 $ (215,346 ) $ 2,743,050 $ 12,371,177 $ (1,263,664 ) $ 13,845,454 Total gains/(losses) realized and unrealized: Included in earnings 21,066 (1,009 ) 20,640 14,490 701,562 (922,849 ) (166,100 ) Included in other comprehensive income (48,611 ) — — (77,645 ) (311,773 ) 35,303 (402,726 ) Purchases 234,880 — — — — — 234,880 Issuances — — — — — — — Sales — — — — — — — Settlements (21,747 ) (1,705 ) 4,430 — (252,782 ) 7,678 (264,126 ) Transfers into Level 3 — — 88,218 — — — 88,218 Transfers out of Level 3 — — — — — — — Deconsolidation of VIEs — — — — (325,123 ) — (325,123 ) Balance, end of period $ 383,789 $ 9,322 $ (102,058 ) $ 2,679,895 $ 12,183,061 $ (2,143,532 ) $ 13,010,477 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ — $ (1,009 ) $ (20,081 ) $ 14,490 $ 760,059 $ (970,656 ) $ (217,197 ) Nine Months Ended September 30, 2014: Balance, beginning of period $ 67,783 $ 13,384 $ (186,934 ) $ 2,475,182 $ 13,398,895 $ (1,514,605 ) $ 14,253,705 Total gains/(losses) realized and unrealized: Included in earnings 1,676 (983 ) (36,323 ) 235,178 735,597 (268,951 ) 666,194 Included in other comprehensive income (595 ) — — (58,677 ) (270,727 ) 24,066 (305,933 ) Purchases — — — — 70,000 — 70,000 Issuances — — — — — — — Sales (3,388 ) — — — — — (3,388 ) Settlements (2,608 ) — 7,355 — (733,492 ) 433,896 (294,849 ) Transfers into Level 3 — — — — — — — Transfers out of Level 3 (208 ) — — — (696,789 ) 36,891 (660,106 ) Balance, end of period $ 62,660 $ 12,401 $ (215,902 ) $ 2,651,683 $ 12,503,484 $ (1,288,703 ) $ 13,725,623 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ — $ (983 ) $ (39,830 ) $ 235,178 $ 736,732 $ (264,899 ) $ 666,198 The tables below provide roll-forward information by class of investments and derivatives measured using significant unobservable inputs. Level 3 - Investments by Class: Other Asset Corporate U.S. Agency Non-Agency Total Three Months Ended September 30, 2015: Balance, beginning of period $ — $ — $ — $ 380,332 $ 380,332 Total gains/(losses) realized and unrealized: Included in earnings — — — 8,429 8,429 Included in other comprehensive income — — — (4,288 ) (4,288 ) Purchases — — — 28 28 Issuances — — — — — Sales — — — — — Settlements — — — (712 ) (712 ) Transfers into Level 3 — — — — — Transfers out of Level 3 — — — — — Balance, end of period $ — $ — $ — $ 383,789 $ 383,789 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ — $ — $ — $ — $ — Three Months Ended September 30, 2014: Balance, beginning of period $ 62,601 $ 3,751 $ — $ — $ 66,352 Total gains/(losses) realized and unrealized: Included in earnings 859 (24 ) — — 835 Included in other comprehensive income (272 ) 18 — — (254 ) Purchases — — — — — Issuances — — — — — Sales (3,388 ) — — — (3,388 ) Settlements (885 ) — — — (885 ) Transfers into Level 3 — — — — — Transfers out of Level 3 — — — — — Balance, end of period $ 58,915 $ 3,745 $ — $ — $ 62,660 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ — $ — $ — $ — $ — Level 3 - Investments by Class: Other Asset Corporate U.S. Agency Non-Agency Total Nine Months Ended September 30, 2015: Balance, beginning of period $ — $ 3,808 $ — $ 194,393 $ 198,201 Additions of VIEs consolidated — — — — — Total gains/(losses) realized and unrealized: Included in earnings — (19 ) — 21,085 21,066 Included in other comprehensive income — (286 ) — (48,325 ) (48,611 ) Purchases — — — 234,880 234,880 Issuances — — — — — Sales — — — — — Settlements — (3,503 ) — (18,244 ) (21,747 ) Transfers into Level 3 — — — — — Transfers out of Level 3 — — — — — Balance, end of period $ — $ — $ — $ 383,789 $ 383,789 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ — $ — $ — $ — $ — Nine Months Ended September 30, 2014: Balance, beginning of period $ 64,073 $ 3,502 $ 208 $ — $ 67,783 Additions of VIEs consolidated — — — — — Total gains/(losses) realized and unrealized: Included in earnings 1,748 (72 ) — — 1,676 Included in other comprehensive income (910 ) 315 — — (595 ) Purchases — — — — — Issuances — — — — — Sales (3,388 ) — — — (3,388 ) Settlements (2,608 ) — — — (2,608 ) Transfers into Level 3 — — — — — Transfers out of Level 3 — — (208 ) — (208 ) Balance, end of period $ 58,915 $ 3,745 $ — $ — $ 62,660 The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ — $ — $ — $ — $ — Level 3 - Derivatives by Class: Interest Credit Total Three Months Ended September 30, 2015: Balance, beginning of period $ (52,819 ) $ (66,490 ) $ (119,309 ) Total gains/(losses) realized and unrealized: Included in earnings (16,879 ) 36,952 20,073 Included in other comprehensive income — — — Purchases — — — Issuances — — — Sales — — — Settlements (2,473 ) (349 ) (2,822 ) Transfers into Level 3 — — — Transfers out of Level 3 — — — Balance, end of period $ (72,171 ) $ (29,887 ) $ (102,058 ) The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ (16,879 ) $ 4,594 $ (12,285 ) Three Months Ended September 30, 2014: Balance, beginning of period $ (129,010 ) $ (89,651 ) $ (218,661 ) Total gains/(losses) realized and unrealized: Included in earnings (3,532 ) 7,417 3,885 Included in other comprehensive income — — — Purchases — — — Issuances — — — Sales — — — Settlements (530 ) (596 ) (1,126 ) Transfers into Level 3 — — — Transfers out of Level 3 — — — Balance, end of period $ (133,072 ) $ (82,830 ) $ (215,902 ) The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ (3,532 ) $ 6,761 $ 3,229 Level 3 - Derivatives by Class: Interest Credit Total Nine Months Ended September 30, 2015: Balance, beginning of period $ (141,887 ) $ (73,459 ) $ (215,346 ) Total gains/(losses) realized and unrealized: Included in earnings (24,106 ) 44,746 20,640 Included in other comprehensive income — — — Purchases — — — Issuances — — — Sales — — — Settlements 5,604 (1,174 ) 4,430 Transfers into Level 3 88,218 — 88,218 Transfers out of Level 3 — — — Balance, end of period $ (72,171 ) $ (29,887 ) $ (102,058 ) The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ (24,106 ) $ 4,025 $ (20,081 ) Nine Months Ended September 30, 2014: Balance, beginning of period $ (92,612 ) $ (94,322 ) $ (186,934 ) Total gains/(losses) realized and unrealized: Included in earnings (49,903 ) 13,580 (36,323 ) Included in other comprehensive income — — — Purchases — — — Issuances — — — Sales — — — Settlements 9,443 (2,088 ) 7,355 Transfers into Level 3 — — — Transfers out of Level 3 — — — Balance, end of period $ (133,072 ) $ (82,830 ) $ (215,902 ) The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ (49,903 ) $ 10,073 $ (39,830 )
Summary of Gains and Losses (Realized and Unrealized) Relating to Level 3 Assets and Liabilities Included in Earnings	Gains and losses (realized and unrealized) relating to Level 3 assets and liabilities included in earnings for the affected periods are reported as follows: Net Realized Unrealized Derivative Income Other Three Months Ended September 30, 2015: Total gains or losses included in earnings for the period $ 8,429 $ 1,693 $ 35,259 $ (16,879 ) $ 24,274 $ (382 ) Changes in unrealized gains or losses relating to the assets and liabilities still held at the reporting date — — 4,594 (16,879 ) 34,964 (382 ) Three Months Ended September 30, 2014: Total gains or losses included in earnings for the period $ 835 $ 596 $ 6,820 $ (3,532 ) $ 297,183 $ (381 ) Changes in unrealized gains or losses relating to the assets and liabilities still held at the reporting date — — 6,761 (3,532 ) 304,365 (381 ) Nine Months Ended September 30, 2015: Total gains or losses included in earnings for the period $ 21,066 $ 2,519 $ 42,227 $ (24,106 ) $ (206,797 ) $ (1,009 ) Changes in unrealized gains or losses relating to the assets and liabilities still held at the reporting date — — 4,025 (24,106 ) (196,107 ) (1,009 ) Nine Months Ended September 30, 2014: Total gains or losses included in earnings for the period $ 1,676 $ 2,088 $ 11,491 $ (49,903 ) $ 701,824 $ (983 ) Changes in unrealized gains or losses relating to the assets and liabilities still held at the reporting date — — 10,074 (49,903 ) 707,011 (983 )

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2015
Investments, Debt and Equity Securities [Abstract]
Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments	The amortized cost and estimated fair value of available-for-sale investments, excluding VIE investments, at September 30, 2015 and December 31, 2014 were as follows: Amortized Gross Gross Estimated Non-credit other- (1) September 30, 2015 Fixed income securities: Municipal obligations $ 420,465 $ 5,217 $ 6,681 $ 419,001 $ — Corporate obligations 1,593,457 11,739 17,618 1,587,578 — Foreign obligations 104,226 1,710 2,282 103,654 — U.S. government obligations 30,410 672 219 30,863 — U.S. agency obligations 4,283 — 2 4,281 — Residential mortgage-backed securities 1,797,616 116,052 42,185 1,871,483 27,439 Collateralized debt obligations 82,734 54 876 81,912 — Other asset-backed securities 836,309 23,109 1,314 858,104 — 4,869,500 158,553 71,177 4,956,876 27,439 Short-term 364,784 — 4 364,780 — 5,234,284 158,553 71,181 5,321,656 27,439 Fixed income securities pledged as collateral: U.S. government obligations 64,556 416 — 64,972 — Total collateralized investments 64,556 416 — 64,972 — Total available-for-sale investments $ 5,298,840 $ 158,969 $ 71,181 $ 5,386,628 $ 27,439 December 31, 2014 Fixed income securities: Municipal obligations $ 523,019 $ 9,769 $ 6,996 $ 525,792 $ — Corporate obligations 1,382,195 12,815 9,416 1,385,594 — Foreign obligations 126,041 3,060 1,344 127,757 — U.S. government obligations 42,328 1,078 427 42,979 — U.S. agency obligations 29,524 — 38 29,486 — Residential mortgage-backed securities 1,557,059 167,396 13,500 1,710,955 7,773 Collateralized debt obligations 21,346 50 274 21,122 — Other asset-backed securities 833,366 48,794 159 882,001 — 4,514,878 242,962 32,154 4,725,686 7,773 Short-term 360,069 — 4 360,065 — 4,874,947 242,962 32,158 5,085,751 7,773 Fixed income securities pledged as collateral: U.S. government obligations 64,378 — 111 64,267 — Total collateralized investments 64,378 — 111 64,267 — Total available-for-sale investments $ 4,939,325 $ 242,962 $ 32,269 $ 5,150,018 $ 7,773 (1) Represents the amount of non-credit other-than-temporary impairment losses remaining in accumulated other comprehensive loss on securities that also had a credit impairment. These losses are included in gross unrealized losses as of September 30, 2015 and December 31, 2014 .
Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments Held by Successor Ambac, by Contractual Maturity	The amortized cost and estimated fair value of available-for-sale investments, excluding VIE investments, at September 30, 2015 , by contractual maturity, were as follows: Amortized Estimated Due in one year or less $ 534,324 $ 534,445 Due after one year through five years 900,319 899,172 Due after five years through ten years 967,158 961,706 Due after ten years 180,380 179,806 2,582,181 2,575,129 Residential mortgage-backed securities 1,797,616 1,871,483 Collateralized debt obligations 82,734 81,912 Other asset-backed securities 836,309 858,104 Total $ 5,298,840 $ 5,386,628
Summary of Gross Unrealized Losses and Fair Values of Ambac's Available-for-Sale Investments	The following table shows gross unrealized losses and fair values of Ambac’s available-for-sale investments, aggregated by investment category and length of time that the individual securities have been in a continuous unrealized loss position, at September 30, 2015 and December 31, 2014 : Less Than 12 Months 12 Months or More Total Fair Value Gross Fair Value Gross Fair Value Gross September 30, 2015 Fixed income securities: Municipal obligations $ 91,214 $ 1,751 $ 124,358 $ 4,930 $ 215,572 $ 6,681 Corporate obligations 677,529 15,731 104,242 1,887 781,771 17,618 Foreign obligations 33,646 1,389 7,842 893 41,488 2,282 U.S. government obligations 4,671 150 10,789 69 15,460 219 U.S. agency obligations — — 4,281 2 4,281 2 Residential mortgage-backed securities 626,063 37,165 73,204 5,020 699,267 42,185 Collateralized debt obligations 73,563 876 — — 73,563 876 Other asset-backed securities 428,610 1,285 16,494 29 445,104 1,314 1,935,296 58,347 341,210 12,830 2,276,506 71,177 Short-term 18,822 4 — — 18,822 4 1,954,118 58,351 341,210 12,830 2,295,328 71,181 Fixed income securities, pledged as collateral: U. S. government obligations — — — — — — Total collateralized investments — — — — — — Total temporarily impaired securities $ 1,954,118 $ 58,351 $ 341,210 $ 12,830 $ 2,295,328 $ 71,181 Less Than 12 Months 12 Months or More Total Fair Value Gross Fair Value Gross Fair Value Gross December 31, 2014: Fixed income securities: Municipal obligations $ 77,788 $ 1,244 $ 135,076 $ 5,752 $ 212,864 $ 6,996 Corporate obligations 453,504 4,998 172,045 4,418 625,549 9,416 Foreign obligations 20,827 748 14,277 596 35,104 1,344 U.S. government obligations 7,223 154 14,735 273 21,958 427 U.S. agency obligations 25,039 2 4,378 36 29,417 38 Residential mortgage-backed securities 413,203 12,391 10,076 1,109 423,279 13,500 Collateralized debt obligations 5,012 274 — — 5,012 274 Other asset-backed securities 248,823 155 68 4 248,891 159 1,251,419 19,966 350,655 12,188 1,602,074 32,154 Short-term 8,803 4 — — 8,803 4 1,260,222 19,970 350,655 12,188 1,610,877 32,158 Fixed income securities, pledged as collateral: U. S. government obligations 64,267 111 — — 64,267 111 Total collateralized investments 64,267 111 — — 64,267 111 Total temporarily impaired securities $ 1,324,489 $ 20,081 $ 350,655 $ 12,188 $ 1,675,144 $ 32,269
Summary of Amounts Included in Net Realized (Losses) Gains and Other-Than-Temporary Impairments	The following table details amounts included in net realized gains and other-than-temporary impairments included in earnings for the affected periods: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Gross realized gains on securities $ 343 $ 7,658 $ 54,484 $ 37,355 Gross realized losses on securities (2,463 ) (3,908 ) (7,431 ) (7,779 ) Net foreign exchange gains (losses) 4,226 6,295 3,801 (175 ) Net realized gains $ 2,106 $ 10,045 $ 50,854 $ 29,401 Net other-than-temporary impairments (1) $ (9,150 ) $ (5,011 ) $ (13,289 ) $ (24,157 ) (1) Other-than-temporary impairments exclude impairment amounts recorded in other comprehensive income under ASC Paragraph 320-10-65-1, which comprise non-credit related amounts on securities that are credit impaired but which management does not intend to sell and it is not more likely than not that Ambac will be required to sell before recovery of the amortized cost basis.
Summary of Roll-Forward of Ambac's Cumulative Credit Losses on Debt Securities for Which Portion of Other-than-Temporary Impairment was Recognized in Other Comprehensive Income	The following table presents a roll-forward of Ambac’s cumulative credit losses on debt securities held as of September 30, 2015 and 2014 for which a portion of an other-than-temporary impairment was recognized in other comprehensive income: Nine Months Ended September 30, 2015 2014 Balance, beginning of period $ 14,062 $ 1,182 Additions for credit impairments recognized on: Securities not previously impaired 7,172 11,337 Securities previously impaired 4,059 — Reductions for credit impairments previously recognized on: Securities that matured or were sold during the period — — Balance, end of period $ 25,293 $ 12,519
Summary of Sources of Collateral Received and Various Investment Agreement in which Collateral Pledged	The following table presents (i) the sources of collateral either received from various counterparties where Ambac is permitted to sell or re-pledge the collateral or collateral held directly in the investment portfolio and (ii) how that collateral was pledged to various investment agreement, derivative and repurchase agreement counterparties at September 30, 2015 and December 31, 2014 : Fair Value of Cash Fair Value of Cash Fair Value of Cash September 30, 2015: Sources of Collateral: Cash and securities pledged directly from the investment portfolio $ 348,584 $ 108,398 $ 240,186 December 31, 2014: Sources of Collateral: Cash and securities pledged directly from the investment portfolio $ 379,423 $ 156,916 $ 222,507
Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities	The following table represents the fair value, including the value of the financial guarantee, and weighted-average underlying rating, excluding the financial guarantee, of the insured securities at September 30, 2015 and December 31, 2014 , respectively: Municipal Corporate Mortgage Total Weighted (1) September 30, 2015: Ambac Assurance Corporation (2) $ 53,097 $ — $ 2,119,005 $ 2,172,102 CCC- Assured Guaranty Municipal Corporation 58,794 — — 58,794 A+ National Public Finance Guarantee Corporation 48,695 — — 48,695 A- MBIA Insurance Corporation — 29,108 — 29,108 A+ Total $ 160,586 $ 29,108 $ 2,119,005 $ 2,308,699 CCC December 31, 2014: Ambac Assurance Corporation (2) $ 53,164 $ — $ 2,146,555 $ 2,199,719 CCC- Assured Guaranty Municipal Corporation 119,492 — — 119,492 A National Public Finance Guarantee Corporation 67,895 — — 67,895 A- MBIA Insurance Corporation — 32,460 — 32,460 A+ Total $ 240,551 $ 32,460 $ 2,146,555 $ 2,419,566 CCC (1) Ratings are based on the lower of Standard & Poor’s or Moody’s rating. If unavailable, Ambac’s internal rating is used. (2) Includes asset-backed securities with a fair value of $78,925 and $51,395 at September 30, 2015 and December 31, 2014 , insured by Ambac UK .
Summary of Net Investment Income	Net investment income was comprised of the following for the affected periods: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Fixed income securities $ 67,293 $ 84,339 $ 197,506 $ 233,878 Short-term investments 85 832 186 2,000 Loans 113 123 338 415 Investment expense (1,872 ) (2,413 ) (6,801 ) (7,723 ) Securities available-for-sale and short-term 65,619 82,881 191,229 228,570 Other investments (1,424 ) 700 10,702 5,905 Total net investment income $ 64,195 $ 83,581 $ 201,931 $ 234,475 Net investment income from Other investments primarily represents changes in fair value on securities classified as trading or under the fair value option plus, for periods after August 28, 2014, income from Ambac's equity interest in an unconsolidated trust created in connection with its sale of Segregated Account junior surplus notes on that date. The portion of net unrealized gains (losses) related to trading securities still held at the end of each period is as follows: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Net gains (losses) recognized during the period on trading securities $ (2,549 ) $ 329 $ 7,493 $ 5,534 Less: net gains (losses) recognized during the reporting period on trading securities sold during the period 933 — 7,534 (431 ) Unrealized gains (losses)recognized during the reporting period on trading securities still held at the reporting date $ (3,482 ) $ 329 $ (41 ) $ 5,965

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2015
Summary of Gross Fair Values of Individual Derivative Instruments	The following tables summarize the gross fair values of individual derivative instruments and the impact of legal rights of offset as reported in the Consolidated Balance Sheets as of September 30, 2015 and December 31, 2014 : Gross Gross Net Amounts Gross Net Amount September 30, 2015: Derivative Assets: Credit derivatives $ 1,345 $ — $ 1,345 $ — $ 1,345 Interest rate swaps 153,528 63,785 89,743 — 89,743 Futures contracts — — — — — Total non-VIE derivative assets $ 154,873 $ 63,785 $ 91,088 $ — $ 91,088 Derivative Liabilities: Credit derivatives $ 31,232 $ — $ 31,232 $ — $ 31,232 Interest rate swaps 408,168 63,785 344,383 186,752 157,631 Futures contracts 220 — 220 — 220 Total non-VIE derivative liabilities $ 439,620 $ 63,785 $ 375,835 $ 186,752 $ 189,083 VIE derivative assets: Interest rate swaps $ — $ — $ — $ — $ — Currency swaps 31,429 31,429 — — — Total VIE derivative assets $ 31,429 $ 31,429 $ — $ — $ — VIE derivative liabilities: Interest rate swaps $ 2,065,224 $ — $ 2,065,224 $ — $ 2,065,224 Currency swaps — 31,429 (31,429 ) — (31,429 ) Total VIE derivative liabilities $ 2,065,224 $ 31,429 $ 2,033,795 $ — $ 2,033,795 December 31, 2014: Derivative Assets: Credit derivatives $ 2,043 $ — $ 2,043 $ — $ 2,043 Interest rate swaps 161,640 54,666 106,974 — 106,974 Total non-VIE derivative assets $ 163,683 $ 54,666 $ 109,017 $ — $ 109,017 Derivative Liabilities: Credit derivatives $ 75,502 $ — $ 75,502 $ — $ 75,502 Interest rate swaps 385,546 54,666 330,880 169,573 161,307 Futures contracts 562 — 562 562 — Total non-VIE derivative liabilities $ 461,610 $ 54,666 $ 406,944 $ 170,135 $ 236,809 Variable Interest Entities: Interest rate swaps $ 2,133,268 $ — $ 2,133,268 $ — $ 2,133,268 Currency swaps 66,895 — 66,895 — 66,895 Total VIE derivative liabilities $ 2,200,163 $ — $ 2,200,163 $ — $ 2,200,163
Summary of Location and Amount of Gains and Losses of Derivative Contracts	There were no amounts held representing an obligation to return cash collateral as of September 30, 2015 and December 31, 2014 . The following tables summarize the location and amount of gains and losses of derivative contracts in the Consolidated Statements of Total Comprehensive Income for the three and nine months ended September 30, 2015 and 2014 : Location of Gain or (Loss) Recognized in Consolidated Statements of Total Comprehensive Income Amount of Gain or (Loss) Recognized in Consolidated Statement of Total Comprehensive Income Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Financial Guarantee: Credit derivatives Net change in fair value of credit derivatives $ 36,952 $ 7,416 $ 44,746 $ 13,579 Financial Services derivatives products: Interest rate swaps Derivative products (63,044 ) (15,638 ) (48,839 ) (112,995 ) Futures contracts Derivative products (2,039 ) (47 ) (3,019 ) (4,516 ) Total Financial Services derivative products (65,083 ) (15,685 ) (51,858 ) (117,511 ) Variable Interest Entities: Currency swaps Income (loss) on variable interest entities 12,235 17,014 53,552 21,425 Interest rate swaps Income (loss) on variable interest entities (15,793 ) (44,846 ) 68,044 (204,411 ) Total Variable Interest Entities (3,558 ) (27,832 ) 121,596 (182,986 ) Total derivative contracts $ (31,689 ) $ (36,101 ) $ 114,484 $ (286,918 )
Summary of Gross Principal Notional Outstanding for CDS Contracts	The following tables summarize the gross principal notional outstanding for CDS contracts, by Ambac rating, for each major category as of September 30, 2015 and December 31, 2014 : CLO Other Total Ambac Rating - September 30, 2015: AAA $ — $ — $ — AA 341,668 233,231 574,899 A — 9,322 9,322 BBB (1) — 469,724 469,724 Below investment grade (2) — 259,852 259,852 Total $ 341,668 $ 972,129 $ 1,313,797 Ambac Rating - December 31, 2014: AAA $ — $ — $ — AA 549,923 217,680 767,603 A — 43,160 43,160 BBB (1) — 448,249 448,249 Below investment grade (2) — 270,747 270,747 Total $ 549,923 $ 979,836 $ 1,529,759 (1) BBB internal ratings reflect bonds which are of medium grade credit quality with adequate capacity to pay interest and repay principal. Certain protective elements and margins may weaken under adverse economic conditions and changing circumstances. These bonds are more likely than higher rated bonds to exhibit unreliable protection levels over all cycles. (2) Below investment grade internal ratings reflect bonds which are of speculative grade credit quality with the adequacy of future margin levels for payment of interest and repayment of principal potentially adversely affected by major ongoing uncertainties or exposure to adverse conditions.
Summarize Information by Major Category of CDS Contracts	The tables below summarize information by major category as of September 30, 2015 and December 31, 2014 : CLO Other Total September 30, 2015: Number of CDS transactions 5 9 14 Gross principal notional outstanding $ 341,668 $ 972,129 $ 1,313,797 Net derivative liabilities at fair value $ 1,740 $ 28,147 $ 29,887 December 31, 2014: Number of CDS transactions 6 10 16 Gross principal notional outstanding $ 549,923 $ 979,836 $ 1,529,759 Net derivative liabilities at fair value $ 2,027 $ 71,432 $ 73,459
Summary of Notional Amounts of AFS's Trading Derivative Products	As of September 30, 2015 and December 31, 2014 the notional amounts of AFS’s trading derivative products are as follows: Notional Type of derivative September 30, December 31, Interest rate swaps—receive-fixed/pay-variable $ 757,135 $ 782,904 Interest rate swaps—pay-fixed/receive-variable 1,446,248 1,479,650 Interest rate swaps—basis swaps 38,965 55,800 Futures contracts 75,000 80,000
Variable Interest Entity, Not Primary Beneficiary, Aggregated Disclosure [Member]
Summary of Notional Amounts of AFS's Trading Derivative Products	The notional for VIE derivatives outstanding as of September 30, 2015 and December 31, 2014 are as follows: Notional Type of VIE derivative September 30, December 31, Interest rate swaps—receive-fixed/pay-variable $ 1,659,640 $ 1,710,344 Interest rate swaps—pay-fixed/receive-variable 3,058,644 3,152,090 Currency swaps 378,050 724,656 Credit derivatives 16,035 18,278

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Major Jurisdictions	The following are the major jurisdictions in which Ambac and its subsidiaries operate and the earliest tax years subject to examination: Jurisdiction Tax Year United States 2010 New York State 2011 New York City 2011 United Kingdom 2009 Italy 2009
Significant Portions of Deferred Tax Liabilities and Deferred Tax Assets	The tax effects of temporary differences that give rise to significant portions of the deferred tax liabilities and deferred tax assets at September 30, 2015 and December 31, 2014 are presented below: September 30, December 31, Deferred tax liabilities: Insurance intangible $ 447,807 $ 493,822 Variable interest entities 15,615 14,149 Investments 147,881 138,072 Unearned premiums and credit fees 99,372 104,589 Other 33,768 33,835 Total deferred tax liabilities 744,443 784,467 Deferred tax assets: Net operating loss and capital carryforward 1,691,018 1,890,551 Loss reserves 119,427 185,881 Compensation 6,016 5,276 AMT Credits 18,439 10,359 Other 9,540 9,539 Sub total deferred tax assets 1,844,440 2,101,606 Valuation allowance 1,101,954 1,319,218 Total deferred tax assets 742,486 782,388 Net deferred tax asset (liability) $ (1,957 ) $ (2,079 )

Commitments and Contingencies E

Commitments and Contingencies Estimate of Future Net Minimum Lease Payments (Tables)	9 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Estimate of Future Net Minimum Lease Payments	An estimate of future net minimum lease payments in each of the next five years ending December 31, and the periods thereafter, is as follows: 2015 (1) 2016 2017 2018 2019 Thereafter Total Operating lease obligations $ 1,375 $ 6,168 $ 6,168 $ 6,168 $ 5,046 $ 14,947 $ 39,872 (1) Includes October through December 2015

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Summary of Financial Information by Reportable Segment	The following table is a summary of financial information by reportable business segment for the affected periods: Financial Financial Corporate Inter-segment Consolidated Three Months Ended September 30, 2015: Revenues: Unaffiliated customers (1) $ 152,024 $ (66,997 ) $ 1,538 $ — $ 86,565 Equity in net income of investees accounted for by equity method — — 1,125 — 1,125 Inter-segment 24 (204 ) 252 (72 ) — Total revenues before expenses and reorganization items 152,048 (67,201 ) 2,915 (72 ) 87,690 Pre-tax income (loss): Unaffiliated customers (1)(2)(3) (320,414 ) (67,655 ) (1,249 ) — (389,318 ) Equity in net income of investees accounted for by equity method — — 1,125 — 1,125 Inter-segment (763 ) 425 1,302 (964 ) — Pre-tax income (loss) (321,177 ) (67,230 ) 1,178 (964 ) (388,193 ) Total assets as of September 30, 2015 23,610,582 363,118 289,238 3,981 24,266,919 Net investment income 61,292 139 2,764 — 64,195 Insurance intangible amortization 39,680 — — — 39,680 Interest expense 29,738 161 — — 29,899 Goodwill impairment 514,511 — — — 514,511 Three Months Ended September 30, 2014: Revenues: Unaffiliated customers (1) $ 170,335 $ (15,445 ) $ 78 $ — $ 154,968 Equity in net income of investees accounted for by equity method — — 371 — 371 Inter-segment 237 (219 ) 5,838 (5,856 ) — Total revenues before expenses and reorganization items 170,572 (15,664 ) 6,287 (5,856 ) 155,339 Pre-tax income (loss): Unaffiliated customers (1) (2) (3) 101,975 (16,304 ) (1,269 ) — 84,402 Equity in net income of investees accounted for by equity method — — 371 — 371 Inter-segment (6,441 ) (281 ) 6,722 — — Pre-tax income (loss) 95,534 (16,585 ) 5,824 — 84,773 Total assets as of September 30, 2014 25,926,306 349,411 298,873 16,195 26,590,785 Net investment income 82,978 154 449 — 83,581 Insurance intangible amortization 41,908 — — — 41,908 Interest expense 31,491 350 — — 31,841 (1) Included in both revenues from unaffiliated customers and in pre-tax income (loss) from unaffiliated customers is net investment income. (2) Included in pre-tax income (loss) from unaffiliated customers is interest expense. (3) Included in pre-tax income (loss) from unaffiliated customers is amortization of intangible asset and impairment of goodwill. Such assets were established upon the adoption of Fresh Start on April 30, 2013. Financial Financial Corporate Inter-segment Consolidated Nine Months Ended September 30, 2015: Revenues: Unaffiliated customers (1) $ 521,340 $ (53,566 ) $ 2,951 $ — $ 470,725 Equity in net income of investees accounted for by equity method — — 3,208 — 3,208 Inter-segment 286 (565 ) 388 (109 ) — Total revenues before expenses and reorganization items 521,626 (54,131 ) 6,547 (109 ) 473,933 Pre-tax income (loss): Unaffiliated customers (1)(2)(3) 172,271 (55,861 ) (5,136 ) — 111,274 Equity in net income of investees accounted for by equity method — — 3,208 — 3,208 Inter-segment (2,087 ) (139 ) 3,027 (801 ) — Pre-tax income (loss) 170,184 (56,000 ) 1,099 (801 ) 114,482 Total assets as of September 30, 2015 23,610,582 363,118 289,238 3,981 24,266,919 Net investment income 195,270 401 6,260 — 201,931 Insurance intangible amortization 115,200 — — — 115,200 Interest expense 85,165 815 — — 85,980 Goodwill impairment 514,511 — — — 514,511 Nine Months Ended September 30, 2014: Revenues: Unaffiliated customers (1) $ 437,591 $ (116,294 ) $ 142 $ — $ 321,439 Equity in net income of investees accounted for by equity method — — 371 — 371 Inter-segment 937 (901 ) 23,309 (23,345 ) — Total revenues before expenses and reorganization items 438,528 (117,195 ) 23,822 (23,345 ) 321,810 Pre-tax income (loss): Unaffiliated customers (1) (2) (3) 157,551 (119,287 ) (4,976 ) — 33,288 Equity in net income of investees accounted for by equity method — — 371 — 371 Inter-segment (24,995 ) (1,150 ) 26,145 — — Pre-tax income (loss) 132,556 (120,437 ) 21,540 — 33,659 Total assets as of September 30, 2014 25,926,306 349,411 298,873 16,195 26,590,785 Net investment income 232,995 967 513 — 234,475 Insurance intangible amortization 109,878 — — — 109,878 Interest expense 94,886 1,236 — — 96,122 (1) Included in both revenues from unaffiliated customers and in pre-tax income (loss) from unaffiliated customers is net investment income. (2) Included in pre-tax income (loss) from unaffiliated customers is interest expense. (3) Included in pre-tax income (loss) from unaffiliated customers is amortization of intangible asset and impairment of goodwill. Such assets were established upon the adoption of Fresh Start on April 30, 2013.
Schedule of Gross Premiums Written, Net Premiums Earned and Net Change in Fair Value of Credit Derivatives	The following table summarizes gross premiums written, net premiums earned and the net change in fair value of credit derivatives included in the Financial Guarantee segment by location of risk for the affected periods: Three Months Ended September 30, 2015 Three Months Ended September 30, 2014 Gross Net Net Change in Gross Net Net Change in United States $ (2,386 ) $ 60,402 $ 30,604 $ (15,355 ) $ 44,882 $ 262 United Kingdom 260 8,081 — 1,482 14,309 — Other international (6,584 ) 3,052 6,348 173 5,640 7,154 Total $ (8,710 ) $ 71,535 $ 36,952 $ (13,700 ) $ 64,831 $ 7,416 Nine Months Ended September 30, 2015 Nine Months Ended September 30, 2014 Gross Net Net Change in Gross Net Net Change in United States $ (5,172 ) $ 163,094 $ 39,286 $ (44,266 ) $ 141,472 $ 6,283 United Kingdom 7,295 23,659 — (1,681 ) 55,752 — Other international (20,963 ) 11,379 5,460 (19,005 ) 15,167 7,296 Total $ (18,840 ) $ 198,132 $ 44,746 $ (64,952 ) $ 212,391 $ 13,579

Background and Business Descr32

Background and Business Description - Additional Information (Detail)	9 Months Ended		12 Months Ended
	Sep. 30, 2015USD ($)Segment$ / sharesshares	Sep. 30, 2014USD ($)	Dec. 31, 2014$ / sharesshares	Apr. 30, 2013$ / sharesshares
Background And Basis Of Presentation [Line Items]
Entity Incorporation, Date of Incorporation	Apr. 29, 1991
Number of reportable segments | Segment	2
Investment Warrants Expiration Date			Apr. 30, 2023
Payment of permitted policy claim (percent)			25.00%
Common stock, shares authorized	130,000,000		130,000,000
Common Stock, Par or Stated Value Per Share | $ / shares	$ 0.01		$ 0.01	$ 0.01
Preferred stock, shares authorized	20,000,000		20,000,000
Preferred Stock, Par or Stated Value Per Share | $ / shares	$ 0.01		$ 0.01
Common stock, shares issued	45,036,587		45,005,932
Warrants Distributed In Bankruptcy				5,047,138
Warrants issued exercise price | $ / shares				$ 16.67
Ambac Assurance [Member]
Background And Basis Of Presentation [Line Items]
Net par exposure for policies allocated to the Segregated Account | $	$ 16,595,339,000
Minimum surplus amount | $	100,000,000
Statutory Accounting Practices, Statutory Capital and Surplus, Balance | $	350,559,000
Successor [Member]
Background And Basis Of Presentation [Line Items]
Proceeds from the sale of Junior Surplus Notes of the Segregated Account | $	$ 0	$ 224,262,000
Common stock, shares issued				45,000,000
Warrants Distributed In Bankruptcy				5,047,138

Basis of Presentation and Sig33

Basis of Presentation and Significant Accounting Policies (Details) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Goodwill [Roll Forward]
Beginning balance			$ 514,511	$ 514,511	$ 514,511
Accumulated impairment loss	$ 514,511	$ 0	514,511	0	0
Ending balance	0		0		$ 514,511
Reorganization items	$ 0	$ 2	$ 0	$ 211

Basis of Presentation and Sig34

Basis of Presentation and Significant Accounting Policies Goodwill (Details) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Goodwill	$ 0		$ 0		$ 514,511	$ 514,511
Goodwill, Impairment Loss	$ (514,511)	$ 0	$ (514,511)	$ 0	$ 0

Special Purpose Entities, Inc35

Special Purpose Entities, Including Variable Interest Entities - Additional Information (Detail) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2015USD ($)TransactionsEntity	Sep. 30, 2015USD ($)TransactionsEntity	Dec. 31, 2014USD ($)Entity
Variable Interest Entities [Line Items]
Number of RMBS Sold		17
Cash Received From Delaware Trust		$ 146,000
Number of VIEs AAC Transferred Assets To		2
Number of VIEs Liquidated	1	1
Secured Debt	$ 137,049	$ 137,049
Par Value of Securities Placed in Trust	386,129	386,129
Fair Value of Securities Placed in Trust	403,106	403,106
Securities Issued by Delaware Trust		146,000
Fair value of special purpose entities	9,322	9,322	$ 12,036
Consolidated VIE assets	14,875,442	14,875,442	15,126,110
Consolidated VIE liabilities	$ 14,830,828	14,830,828	15,085,685
variable interest entities deconsolidation gain loss		$ 572
Asset-Backed Securities and Utility Obligations [Member]
Variable Interest Entities [Line Items]
Weighted average life		6 years 9 months 12 days
Average rating of assets held by sponsored special purpose entities		BBB
Sponsored Variable Interest Entities [Member]
Variable Interest Entities [Line Items]
Number of individual transactions with special purpose entities | Transactions	15	15
Number of transactions outstanding with special purpose entities | Transactions	3	3
Total principal amount of debt outstanding	$ 457,960	$ 457,960	$ 457,960
Consolidated Entities [Member]
Variable Interest Entities [Line Items]
Number of DeConsolidated Variable Interest Entities	1	2
Number of consolidated Variable Interest Entities | Entity	15	15	15
London Interbank Offered Rate (LIBOR) [Member]
Variable Interest Entities [Line Items]
Interest Rate on Securities Issued by Delaware Trust		2.80%

Special Purpose Entities, Inc36

Special Purpose Entities, Including Variable Interest Entities - Summary of Fair Value of Fixed Income Securities, by Asset-Type, Held by Consolidated Variable Interest Entities (Detail) - Successor [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investments:
Fixed income securities	$ 5,386,628	$ 5,150,018
Variable Interest Entities [Member]
Investments:
Fixed income securities	2,679,895	2,743,050
Corporate Obligations [Member]
Investments:
Fixed income securities	$ 2,679,895	$ 2,743,050

Special Purpose Entities, Inc37

Special Purpose Entities, Including Variable Interest Entities - Supplemental Information about Loans Held as Assets and Long-Term Debt Associated with Consolidated Variable Interest Entities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Variable Interest Entities [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	$ 14,830,828	$ 15,085,685
Variable Interest Entities [Member] | Successor [Member]
Variable Interest Entities [Line Items]
Loans, Estimated fair value	12,183,061	12,371,177
Long-term debt, Estimated fair value	12,791,012	12,882,076
Loans, Unpaid principal balance	9,446,235	10,236,695
Long-term debt, Unpaid principal balance	$ 11,366,061	$ 11,925,499

Special Purpose Entities, Inc38

Special Purpose Entities, Including Variable Interest Entities - Summary of Carrying Amount of Assets, Liabilities and Maximum Exposure to Loss of Ambac's Variable Interests in Non-Consolidated Variable Interest Entities (Detail) - Variable Interest Entity [Member] - Successor [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	$ 59,454,974
Insurance Assets	1,712,622
Insurance Liabilities	4,467,192
Derivative Liabilities	(145,623)
Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	28,991,240
Insurance Assets	1,284,905
Insurance Liabilities	3,983,686
Derivative Liabilities	(124,202)
Global Public Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	30,463,734	$ 31,639,004
Insurance Assets	427,717	457,774
Insurance Liabilities	483,506	533,192
Derivative Liabilities	(21,421)	(22,135)
Collateralized Debt Obligations [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	1,041,843	1,386,100
Insurance Assets	271	345
Insurance Liabilities	3,716	4,000
Derivative Liabilities	(139,859)	(145,565)
Residential Mortgage-Backed Securities [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	17,722,719	19,464,549
Insurance Assets	1,034,921	1,011,888
Insurance Liabilities	2,740,222	2,924,987
Other Consumer Asset-Backed [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	4,321,282	5,109,776
Insurance Assets	51,802	65,204
Insurance Liabilities	648,958	885,572
Derivative Liabilities	(349)	(36,877)
Other Commercial Asset-Backed [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	2,597,067	3,119,891
Insurance Assets	115,751	135,215
Insurance Liabilities	105,826	128,988
Derivative Liabilities	0	0
Other [Member] | Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	3,308,329	3,801,382
Insurance Assets	82,160	97,345
Insurance Liabilities	484,964	599,915
Derivative Liabilities	$ 16,006	$ 18,176

Comprehensive Income - Schedule

Comprehensive Income - Schedule of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ 95,362	$ 306,328	$ 220,283	$ 11,661
Other comprehensive income before reclassifications	(29,295)	(50,256)	(109,337)	245,035
Amounts reclassified from accumulated other comprehensive income	6,820	(5,207)	(38,059)	(5,831)
Net current period other comprehensive income	(22,475)	(55,463)	(147,396)	239,204
Ending Balance	72,887	250,865	72,887	250,865
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	79,406	231,975	210,693	(41,910)
Other comprehensive income before reclassifications	1,342	(12,222)	(85,313)	261,879
Amounts reclassified from accumulated other comprehensive income	7,040	(5,003)	(37,592)	(5,219)
Net current period other comprehensive income	8,382	(17,225)	(122,905)	256,660
Ending Balance	87,788	214,750	87,788	214,750
Other Postretirement Benefit Plan, Defined Benefit [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	9,784	10,439	10,031	10,847
Other comprehensive income before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income	(220)	(204)	(467)	(612)
Net current period other comprehensive income	(220)	(204)	(467)	(612)
Ending Balance	9,564	10,235	9,564	10,235
Accumulated Translation Adjustment [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	6,172	63,914	(441)	42,724
Other comprehensive income before reclassifications	(30,637)	(38,034)	(24,024)	(16,844)
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Net current period other comprehensive income	(30,637)	(38,034)	(24,024)	(16,844)
Ending Balance	$ (24,465)	$ 25,880	$ (24,465)	$ 25,880

Comprehensive Income - Schedu40

Comprehensive Income - Schedule of Amounts Reclassed Out of Each Component of Accumulated Other Comprehensive Income (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	$ (2,838)	$ (2,344)	$ (8,464)	$ (3,414)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	6,820	(5,207)	(38,059)	(5,831)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized investment gains	7,040	(5,003)	(37,592)	(5,219)
Net of tax and noncontrolling interest	7,040	(5,003)	(37,592)	(5,219)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	7,040	(5,003)	(37,592)	(5,219)
Other Postretirement Benefit Plan, Defined Benefit [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(220)	(204)	(467)	(612)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax and noncontrolling interest	6,820	(5,207)	(38,059)	(5,831)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	0	0	0	0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	0	0	0	0
Prior service cost	(167)	(166)	(500)	(498)
Actuarial gains (losses)	(53)	(38)	33	(114)
Total before tax	(220)	(204)	(467)	(612)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ (220)	$ (204)	$ (467)	$ (612)

Net Income Per Share - Addition

Net Income Per Share - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Apr. 30, 2013
Schedule Of Earnings Per Share [Line Items]
Number of new common stock issued	45,036,587	45,036,587		45,005,932
Par value of common stock issued	$ 0.01	$ 0.01		$ 0.01	$ 0.01
Class of Warrant or Right, Number of Securities Called by Warrants or Rights					5,047,138
Exercise price of common stock					$ 16.67
Investment Warrants Expiration Date				Apr. 30, 2023
Common stock shares issued		236	949
Warrant exercised		740	949
Successor [Member]
Schedule Of Earnings Per Share [Line Items]
Number of new common stock issued					45,000,000
WarrantBuyBackAuthorizedDollars		$ 10,000
Warrants Purchased During Period Shares		577,500
Warrants Purchased During Period Dollars		$ 5,017	$ 0
Class of Warrant or Right, Number of Securities Called by Warrants or Rights					5,047,138
Warrants outstanding	4,461,637	4,461,637
Employee Stock Option [Member] | Successor [Member]
Schedule Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	176,668	110,000
Warrants [Member] | Successor [Member]
Schedule Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	4,461,637
Restricted Stock Units (RSUs) [Member] | Successor [Member]
Schedule Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	78,460
Performance Shares [Member] | Successor [Member]
Schedule Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	96,349

Net Income Per Share - Reconcil

Net Income Per Share - Reconciliation of Common Shares Used for Basic and Diluted Earnings Per Share (Detail) - Successor [Member] - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of common shares used for basic earnings per share	45,174,521	45,115,882	45,173,671	45,083,831
Effect of potential dilutive shares:
Weighted average number of common shares and potential dilutive shares used for diluted earnings per share	45,174,521	46,624,689	46,352,214	47,027,084
Restricted Stock Units (RSUs) [Member]
Effect of potential dilutive shares:
Effect of potential dilutive shares	0	31,384	14,418	40,473
Performance Shares [Member]
Effect of potential dilutive shares:
Effect of potential dilutive shares	0	0	2,729	0
Warrants [Member]
Effect of potential dilutive shares:
Effect of potential dilutive shares	0	1,469,203	1,154,313	1,892,211
Anti-dilutive shares excluded from reconciliation	4,461,637
Employee Stock Option [Member]
Effect of potential dilutive shares:
Effect of potential dilutive shares	0	8,220	7,083	10,569
Anti-dilutive shares excluded from reconciliation	176,668		110,000

Financial Guarantee Insurance43

Financial Guarantee Insurance Contracts - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Insurance [Line Items]
Accumulated amortization on insurance intangible asset	$ 362,404		$ 362,404		$ 249,205
Successor [Member]
Insurance [Line Items]
Estimated Future Premium Payments Weighted Average Discounted Rate	2.70%		2.70%		2.70%
Reinsurance Payable	$ 57,651		$ 57,651		$ 60,436
Weighted average period of future premiums			9 years 8 months 12 days		10 years 1 month 6 days
Transactions with non-investment grade internal ratings			28.00%		32.00%
Non-investment grade RMBS on total premiums receivable			7.00%		7.00%
Uncollectable premium receivables	15,802		$ 15,802		$ 17,780
Past due premiums on policies insuring non-investment grade obligations amount			500
Accelerated premium revenue for retired obligations	28,369	$ 9,192	64,862	$ 42,296
Reinsurance recoveries of losses included in losses and loss expenses	6,907	3,885	30,727	16,045
Losses and loss expense reserves ceded to reinsurers	63,657	105,641	63,657	105,641	100,355
Subrogation recoveries	2,555,461		2,555,461		2,523,540
Subrogation recoveries, net of reinsurance	2,528,260		2,528,260		2,496,515
Intangible amortization expense	39,680	$ 41,908	115,200	$ 109,878
Insurance intangible asset	$ 1,279,448		$ 1,279,448		$ 1,410,920
Percentage of Premiums Receivable Related To Non Investment Grade Lease Securitizations			6.00%		6.00%
Percentage Of Premiums Receivable Related To Non Investment Grade Student Loan Transactions			5.00%		8.00%
Loss Reserves [Member]
Insurance [Line Items]
Weighted average risk-free rate used to discount loss reserves			2.30%		2.30%

Financial Guarantee Insurance44

Financial Guarantee Insurance Contracts - Summary of Gross Premium Receivable Roll-Forward (Direct and Assumed Contracts) (Detail) - Successor [Member] - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Insurance [Line Items]
Percentage Premiums Receivable Related To Transactions With Non Investment Grade Internal Ratings	28.00%		32.00%
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Beginning premium receivable	$ 1,000,607	$ 1,453,021	$ 1,453,021
Premium receipts	(70,940)	(100,646)
Adjustments for changes in expected and contractual cash flows	(39,613)	(93,795)
Accretion of premium receivable discount	18,795	29,644
Uncollectable premiums	1,978	(801)
Other adjustments (including foreign exchange)	(15,381)	(20,791)
Ending premium receivable	$ 895,446	$ 1,266,632	$ 1,000,607
Percentage Of Premiums Receivable Related To Non Investment Grade Rmbs Transactions	7.00%		7.00%
Premiums Receivable, Allowance for Doubtful Accounts	$ 15,802		$ 17,780
Premiums Past Due On Non Investment Grade Obligation	$ 500

Financial Guarantee Insurance45

Financial Guarantee Insurance Contracts - Effect of Reinsurance on Premiums Written and Earned (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct Premiums Written	$ (8,710)	$ (13,700)	$ (18,840)	$ (64,952)
Assumed Reinsurance Premiums Written	0	0	0	0
Ceded Reinsurance Premiums Written	(105)	(2,805)	(882)	(7,316)
Premiums written, net of reinsurance	8,605	10,895	17,958	57,636
Direct Premiums Earned	77,982	68,685	214,787	222,894
Assumed Reinsurance Premiums Earned	22	23	66	114
Ceded Reinsurance Premiums Earned	6,469	3,877	16,721	10,617
Reinsurance on premiums earned, Net	$ 71,535	$ 64,831	$ 198,132	$ 212,391

Financial Guarantee Insurance46

Financial Guarantee Insurance Contracts - Summarized Future Gross Undiscounted Premiums Expected to be Collected, and Future Expected Premiums Earned, Net of Reinsurance (Detail) $ in Thousands	Sep. 30, 2015USD ($)
Insurance [Abstract]
Future premiums expected to be collected, December 31, 2015	$ 21,054
Future premiums expected to be collected, December 31, 2016	82,229
Future premiums expected to be collected, December 31, 2017	76,613
Future premiums expected to be collected, December 31, 2018	71,514
Future premiums expected to be collected, December 31, 2019	67,678
Future premiums expected to be collected, December 31, 2024	298,847
Future premiums expected to be collected, December 31, 2029	248,187
Future premiums expected to be collected, December 31, 2034	174,358
Future premiums expected to be collected, December 31, 2039	63,810
Future premiums expected to be collected, December 31, 2044	23,749
Future premiums expected to be collected, December 31, 2049	9,518
Future premiums expected to be collected, December 31, 2054	1,244
Future premiums expected to be collected, December 31, 2059	5
Future premiums expected to be collected, Total	1,138,806
Future expected premiums to be earned, net of reinsurance, December 31, 2015	36,341
Future expected premiums to be earned, net of reinsurance, December 31, 2016	125,182
Future expected premiums to be earned, net of reinsurance, December 31, 2017	105,390
Future expected premiums to be earned, net of reinsurance, December 31, 2018	94,004
Future expected premiums to be earned, net of reinsurance, December 31, 2019	87,387
Future expected premiums to be earned, net of reinsurance, December 31, 2024	359,221
Future expected premiums to be earned, net of reinsurance, December 31, 2029	255,225
Future expected premiums to be earned, net of reinsurance, December 31, 2034	160,285
Future expected premiums to be earned, net of reinsurance, December 31, 2039	65,206
Future expected premiums to be earned, net of reinsurance, December 31, 2044	22,408
Future expected premiums to be earned, net of reinsurance, December 31, 2049	9,722
Future expected premiums to be earned, net of reinsurance, December 31, 2054	2,183
Future expected premiums to be earned, net of reinsurance, December 31, 2059	3
Future expected premiums to be earned, net of reinsurance, Total	$ 1,322,557

Financial Guarantee Insurance47

Financial Guarantee Insurance Contracts Financial Guarantee Insurance Contracts - Components of Loss and Loss Expense Reserves and Subrogation Recoverable (Details) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered	$ 4,662	$ (130)	$ 4,662	$ (130)	$ (517)
Loss Reserves Ceded To Reinsurers	63,657	105,641	63,657	105,641	100,355
Policyholder Benefits and Claims Incurred, Ceded	(6,907)	(3,885)	(30,727)	(16,045)
Liability for Unpaid Claims and Claims Adjustment Expense, Net		$ 5,408,596		$ 5,408,596
Loss and loss expense reserves	4,237,515		4,237,515		4,752,007
Subrogation recoverable	(982,202)		(982,202)		(953,274)
Claim liability reported on Balance Sheet, before reinsurance	3,255,313		3,255,313		3,798,733
Unpaid Claims-Claims [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Loss and loss expense reserves	2,193,214		2,193,214		2,172,041
Subrogation recoverable	785,993		785,993		772,948
Claim liability reported on Balance Sheet, before reinsurance	2,979,207		2,979,207		2,944,989
Unpaid Claims-Accrued Interest [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Loss and loss expense reserves	324,125		324,125		234,802
Subrogation recoverable	125,225		125,225		94,425
Claim liability reported on Balance Sheet, before reinsurance	449,350		449,350		329,227
Present Value of Expected Net Cash Flows- Claims and Loss Expenses [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Loss and loss expense reserves	3,137,857		3,137,857		3,792,133
Subrogation recoverable	148,147		148,147		197,751
Claim liability reported on Balance Sheet, before reinsurance	3,286,004		3,286,004		3,989,884
Present Value of Expected Net Cash Flows-Recoveries [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Loss and loss expense reserves	(1,238,561)		(1,238,561)		(1,205,621)
Subrogation recoverable	(2,041,567)		(2,041,567)		(2,018,398)
Claim liability reported on Balance Sheet, before reinsurance	(3,280,128)		(3,280,128)		(3,224,019)
Unearned Premium Reserve [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Loss and loss expense reserves	(179,120)		(179,120)		(241,348)
Subrogation recoverable	0		0		0
Claim liability reported on Balance Sheet, before reinsurance	$ (179,120)		$ (179,120)		$ (241,348)

Financial Guarantee Insurance48

Financial Guarantee Insurance Contracts - Summary of Loss Reserve Roll-Forward, Net of Subrogation Recoverable and Reinsurance (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Loss And Loss Adjustment Expense Reserves [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered	$ 4,662	$ (130)	$ 4,662	$ (130)	$ (517)
Policyholder Benefits and Claims Incurred, Ceded	(6,907)	(3,885)	(30,727)	(16,045)
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Less reinsurance on loss and loss expense reserves			100,355
Current year:
ambc_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaimsCurrentYear			1,404	236
Claim and loss expense payments, net of subrogation and reinsurance			0	4
Total current year			1,404	232
Prior years:
Change in previously established loss and loss expense reserves, gross of RMBS subrogation and net of reinsurance			(414,642)	(934)
Claim and loss expense (payments) recoveries, net of subrogation and reinsurance			61,740	(67,736)
Change in previously established RMBS subrogation recoveries, net of reinsurance			(31,744)	(6,315)
Liability For Unpaid Claims And Claims Adjustment Expense Change In Loss Reserves Prior Year			(508,126)	60,487
Net change in loss and loss expense reserves			(506,722)	60,719
Liability for Unpaid Claims and Claims Adjustment Expense, Net		5,408,596		5,408,596
Add reinsurance on loss and loss expense reserves	$ 63,657	105,641	$ 63,657	105,641
Ending gross loss and loss expense reserves		$ 5,514,237		$ 5,514,237

Financial Guarantee Insurance49

Financial Guarantee Insurance Contracts - Summary of Information Related to Policies Currently Included in Ambac's Loss Reserves or Subrogation Recoverable (Detail) - Successor [Member] $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015USD ($)Policies	Dec. 31, 2014USD ($)Policies	Sep. 30, 2014USD ($)	Dec. 31, 2013USD ($)
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	323	325
Remaining weighted-average contract period (in years)	16 years	16 years
Gross insured contractual payments outstanding:
Principal	$ 16,609,211	$ 18,322,914
Interest	6,012,061	7,254,995
Total	22,621,272	25,577,909
Gross undiscounted claim liability	7,856,763	8,679,974
Discount, gross claim liability	1,241,288	1,509,948
Gross claim liability before all subrogation and before reinsurance	6,615,475	7,170,026
Less:
Gross RMBS subrogation	(2,569,094)	(2,541,219)
Discount, RMBS subrogation	13,633	17,679
Discounted RMBS subrogation, before reinsurance	(2,555,461)	(2,523,540)	$ (2,214,430)	$ (2,206,598)
Less:
Gross other subrogation	(801,390)	(792,287)
Discount, other subrogation	76,723	91,808
Discounted other subrogation, before reinsurance	(724,667)	(700,479)
Gross claim liability, net of all subrogation and discounts, before reinsurance	3,335,347	3,946,007
Less: Unearned premium reserves	(179,120)	(241,348)
Plus: Loss adjustment expenses reserves	99,086	94,074
Claim liability reported on Balance Sheet, before reinsurance	3,255,313	3,798,733
Reinsurance recoverable reported on Balance Sheet	$ 68,319	$ 99,838
I/SL [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	44	36
Remaining weighted-average contract period (in years)	7 years	8 years
Gross insured contractual payments outstanding:
Principal	$ 2,099,540	$ 1,026,513
Interest	730,755	418,746
Total	2,830,295	1,445,259
Gross undiscounted claim liability	15,820	16,360
Discount, gross claim liability	786	1,147
Gross claim liability before all subrogation and before reinsurance	15,034	15,213
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	0	0
Discount, other subrogation	0	0
Discounted other subrogation, before reinsurance	0	0
Gross claim liability, net of all subrogation and discounts, before reinsurance	15,034	15,213
Less: Unearned premium reserves	(10,207)	(10,945)
Plus: Loss adjustment expenses reserves	0	3
Claim liability reported on Balance Sheet, before reinsurance	4,827	4,271
Reinsurance recoverable reported on Balance Sheet	$ 641	$ 73
IA [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	17	26
Remaining weighted-average contract period (in years)	17 years	12 years
Gross insured contractual payments outstanding:
Principal	$ 305,681	$ 519,291
Interest	138,831	212,296
Total	444,512	731,587
Gross undiscounted claim liability	6,036	11,525
Discount, gross claim liability	596	937
Gross claim liability before all subrogation and before reinsurance	5,440	10,588
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	0	0
Discount, other subrogation	0	0
Discounted other subrogation, before reinsurance	0	0
Gross claim liability, net of all subrogation and discounts, before reinsurance	5,440	10,588
Less: Unearned premium reserves	(2,089)	(3,432)
Plus: Loss adjustment expenses reserves	80	1,303
Claim liability reported on Balance Sheet, before reinsurance	3,431	8,459
Reinsurance recoverable reported on Balance Sheet	$ 895	$ 890
II [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	30	33
Remaining weighted-average contract period (in years)	14 years	15 years
Gross insured contractual payments outstanding:
Principal	$ 1,338,428	$ 3,091,744
Interest	356,410	1,878,770
Total	1,694,838	4,970,514
Gross undiscounted claim liability	46,817	155,488
Discount, gross claim liability	12,179	16,438
Gross claim liability before all subrogation and before reinsurance	34,638	139,050
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	(12,719)	(18,034)
Discount, other subrogation	3,538	6,069
Discounted other subrogation, before reinsurance	(9,181)	(11,965)
Gross claim liability, net of all subrogation and discounts, before reinsurance	25,457	127,085
Less: Unearned premium reserves	(17,961)	(73,749)
Plus: Loss adjustment expenses reserves	819	1,968
Claim liability reported on Balance Sheet, before reinsurance	8,315	55,304
Reinsurance recoverable reported on Balance Sheet	$ 67	$ 1,355
III [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	65	69
Remaining weighted-average contract period (in years)	19 years	21 years
Gross insured contractual payments outstanding:
Principal	$ 3,913,273	$ 3,792,559
Interest	2,940,877	2,765,537
Total	6,854,150	6,558,096
Gross undiscounted claim liability	1,639,016	2,040,402
Discount, gross claim liability	524,462	716,812
Gross claim liability before all subrogation and before reinsurance	1,114,554	1,323,590
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	(133,640)	(127,143)
Discount, other subrogation	35,910	36,779
Discounted other subrogation, before reinsurance	(97,730)	(90,364)
Gross claim liability, net of all subrogation and discounts, before reinsurance	1,016,824	1,233,226
Less: Unearned premium reserves	(86,842)	(88,332)
Plus: Loss adjustment expenses reserves	18,708	6,470
Claim liability reported on Balance Sheet, before reinsurance	948,690	1,151,364
Reinsurance recoverable reported on Balance Sheet	$ 82,496	$ 110,957
IV [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	164	160
Remaining weighted-average contract period (in years)	14 years	12 years
Gross insured contractual payments outstanding:
Principal	$ 8,897,699	$ 9,892,760
Interest	1,827,031	1,979,627
Total	10,724,730	11,872,387
Gross undiscounted claim liability	6,076,327	6,456,139
Discount, gross claim liability	697,119	774,611
Gross claim liability before all subrogation and before reinsurance	5,379,208	5,681,528
Less:
Gross RMBS subrogation	(2,569,094)	(2,541,219)
Discount, RMBS subrogation	13,633	17,679
Discounted RMBS subrogation, before reinsurance	(2,555,461)	(2,523,540)
Less:
Gross other subrogation	(641,812)	(647,110)
Discount, other subrogation	33,468	48,960
Discounted other subrogation, before reinsurance	(608,344)	(598,150)
Gross claim liability, net of all subrogation and discounts, before reinsurance	2,215,403	2,559,838
Less: Unearned premium reserves	(61,546)	(64,890)
Plus: Loss adjustment expenses reserves	79,479	84,330
Claim liability reported on Balance Sheet, before reinsurance	2,233,336	2,579,278
Reinsurance recoverable reported on Balance Sheet	$ (15,780)	$ (13,437)
V [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies	3	1
Remaining weighted-average contract period (in years)	6 years	6 years
Gross insured contractual payments outstanding:
Principal	$ 54,590	$ 47
Interest	18,157	19
Total	72,747	66
Gross undiscounted claim liability	72,747	60
Discount, gross claim liability	6,146	3
Gross claim liability before all subrogation and before reinsurance	66,601	57
Less:
Gross RMBS subrogation	0	0
Discount, RMBS subrogation	0	0
Discounted RMBS subrogation, before reinsurance	0	0
Less:
Gross other subrogation	(13,219)	0
Discount, other subrogation	3,807	0
Discounted other subrogation, before reinsurance	(9,412)	0
Gross claim liability, net of all subrogation and discounts, before reinsurance	57,189	57
Less: Unearned premium reserves	(475)	0
Plus: Loss adjustment expenses reserves	0	0
Claim liability reported on Balance Sheet, before reinsurance	56,714	57
Reinsurance recoverable reported on Balance Sheet	$ 0	$ 0

Financial Guarantee Insurance50

Financial Guarantee Insurance Contracts - Summary of Information Related to Policies Currently Included in Ambac's Loss Reserves or Subrogation Recoverable (Parenthetical) (Detail) - Successor [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Loss Reserves Ceded To Reinsurers	$ 63,657	$ 100,355	$ 105,641
Loss and loss expense reserves	4,237,515	4,752,007
Subrogation recoverable	(982,202)	(953,274)
Liability for Claims			5,514,237
Ceded Loss And Loss Expenses Paid Not Yet Recovered	$ 4,662	$ (517)	$ (130)

Financial Guarantee Insurance51

Financial Guarantee Insurance Contracts - Summary of Balance of RMBS Subrogation Recoveries and Related Claim Liabilities, by Estimation Approach (Detail) - Successor [Member] - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Balance Of Rmbs Subrogation Recoveries And Related Claim Liabilities By Estimation Approach [Line Items]
Subrogation recoveries	$ 2,555,461	$ 2,214,430	$ 2,523,540	$ 2,206,598
Additional Transactions Reviewed Changes in RMBS Subrogation		24,565
Changes in Estimation Approach In Rmbs Subrogation		53,851
Impact Of Sponsor Actions In Residential Mortgage Backed Securities Subrogation	0	(90,000)
Other Changes Rmbs Subrogation	31,921	19,416
Random Samples [Member]
Schedule Of Balance Of Rmbs Subrogation Recoveries And Related Claim Liabilities By Estimation Approach [Line Items]
Gross loss reserve before subrogation recoveries	1,856,754		1,897,426
Subrogation recoveries	2,555,461		2,523,540
Gross loss reserve after subrogation recoveries	(698,707)		(626,114)
Adverse Samples [Member]
Schedule Of Balance Of Rmbs Subrogation Recoveries And Related Claim Liabilities By Estimation Approach [Line Items]
Subrogation recoveries	0	0	0	1,252,773
Additional Transactions Reviewed Changes in RMBS Subrogation		0
Changes in Estimation Approach In Rmbs Subrogation		(1,218,681)
Impact Of Sponsor Actions In Residential Mortgage Backed Securities Subrogation	0	0
Other Changes Rmbs Subrogation	0	(34,092)
Random Samples [Member]
Schedule Of Balance Of Rmbs Subrogation Recoveries And Related Claim Liabilities By Estimation Approach [Line Items]
Subrogation recoveries	2,555,461	2,214,430	$ 2,523,540	$ 953,825
Additional Transactions Reviewed Changes in RMBS Subrogation		24,565
Changes in Estimation Approach In Rmbs Subrogation		1,272,532
Impact Of Sponsor Actions In Residential Mortgage Backed Securities Subrogation	0	(90,000)
Other Changes Rmbs Subrogation	$ 31,921	$ 53,508

Financial Guarantee Insurance52

Financial Guarantee Insurance Contracts - Summary of Rollforward of RMBS Subrogation, by Estimation Approach (Detail) - Successor [Member] - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Subrogation By Estimation Approach [Roll Forward]
Discounted RMBS subrogation (gross of reinsurance), beginning balance	$ 2,523,540	$ 2,206,598
Changes recognized
Additional Transactions Reviewed Changes in RMBS Subrogation		24,565
Changes in Estimation Approach In Rmbs Subrogation		53,851
Impact of sponsor actions	0	(90,000)
Other Changes Rmbs Subrogation	31,921	19,416
Discounted RMBS subrogation (gross of reinsurance), ending balance	2,555,461	2,214,430
Random Samples [Member]
Subrogation By Estimation Approach [Roll Forward]
Discounted RMBS subrogation (gross of reinsurance), beginning balance	2,523,540	953,825
Changes recognized
Additional Transactions Reviewed Changes in RMBS Subrogation		24,565
Changes in Estimation Approach In Rmbs Subrogation		1,272,532
Impact of sponsor actions	0	(90,000)
Other Changes Rmbs Subrogation	31,921	53,508
Discounted RMBS subrogation (gross of reinsurance), ending balance	2,555,461	2,214,430
Adverse Samples [Member]
Subrogation By Estimation Approach [Roll Forward]
Discounted RMBS subrogation (gross of reinsurance), beginning balance	0	1,252,773
Changes recognized
Additional Transactions Reviewed Changes in RMBS Subrogation		0
Changes in Estimation Approach In Rmbs Subrogation		(1,218,681)
Impact of sponsor actions	0	0
Other Changes Rmbs Subrogation	0	(34,092)
Discounted RMBS subrogation (gross of reinsurance), ending balance	$ 0	$ 0

Financial Guarantee Insurance53

Financial Guarantee Insurance Contracts - Estimated Future Amortization Expense for Insurance Intangible Asset (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Amortization Of Intangible Assets [Line Items]
Intangible Assets, Gross (Excluding Goodwill)	$ 1,641,852		$ 1,641,852		$ 1,660,125
Accumulated amortization on insurance intangible asset	362,404		362,404		$ 249,205
2,015	29,892		29,892
2,016	110,315		110,315
2,017	97,714		97,714
2,018	89,267		89,267
2,019	82,506		82,506
Thereafter	869,754		869,754
Successor [Member]
Amortization Of Intangible Assets [Line Items]
Amortization of insurance intangible assets	$ 39,680	$ 41,908	$ 115,200	$ 109,878

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Carrying Amount and Fair Value of Ambac's Financial Assets and Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financial assets:
Other investments	$ 290,723	$ 240,969
Other assets	9,322	12,036
Financial liabilities:
Derivative liabilities	29,887	73,459
Successor [Member]
Financial assets:
Fixed income securities	5,386,628	5,150,018
Short term investments	364,780	360,065
Successor [Member] | Total Fair Value [Member]
Financial assets:
Other investments	302,791	349,468
Cash	27,099	73,903
Loans	5,479	5,634
Total financial assets	20,691,258	20,822,011
Financial liabilities:
Obligations under investment and repurchase agreements	100,858	161,821
Liabilities for net financial guarantees written	3,044,698	4,539,000
Long-term debt	1,318,300	1,379,864
Total financial liabilities	19,664,498	21,569,868
Successor [Member] | Total Fair Value [Member] | Variable Interest Entity [Member]
Financial assets:
Restricted cash	5,895	7,708
Loans	12,183,061	12,371,177
Financial liabilities:
Long-term debt	12,791,012	12,882,076
Successor [Member] | Carrying Amount [Member]
Financial assets:
Other investments	314,934	357,016
Cash	27,099	73,903
Loans	5,499	5,714
Total financial assets	20,703,421	20,829,639
Financial liabilities:
Obligations under investment and repurchase agreements	100,358	160,079
Liabilities for net financial guarantees written	2,414,692	2,923,652
Long-term debt	1,457,996	1,273,805
Total financial liabilities	19,173,688	19,846,719
Successor [Member] | Carrying Amount [Member] | Variable Interest Entity [Member]
Financial assets:
Restricted cash	5,895	7,708
Loans	12,183,061	12,371,177
Financial liabilities:
Long-term debt	12,791,012	12,882,076
Successor [Member] | Level 1 [Member]
Financial assets:
Other investments	0	0
Cash	27,099	73,903
Loans	0	0
Total financial assets	434,779	547,047
Financial liabilities:
Obligations under investment and repurchase agreements	0	0
Liabilities for net financial guarantees written	0	0
Long-term debt	0	0
Total financial liabilities	220	562
Successor [Member] | Level 1 [Member] | Variable Interest Entity [Member]
Financial assets:
Restricted cash	5,895	7,708
Loans	0	0
Financial liabilities:
Long-term debt	0	0
Successor [Member] | Level 2 [Member]
Financial assets:
Other investments	290,723	336,013
Cash	0	0
Loans	0	0
Total financial assets	4,915,573	4,929,368
Financial liabilities:
Obligations under investment and repurchase agreements	0	0
Liabilities for net financial guarantees written	0	0
Long-term debt	139,002	0
Total financial liabilities	13,026,541	14,007,568
Successor [Member] | Level 2 [Member] | Variable Interest Entity [Member]
Financial assets:
Restricted cash	0	0
Loans	0	0
Financial liabilities:
Long-term debt	10,647,480	11,618,412
Successor [Member] | Level 3 [Member]
Financial assets:
Other investments	12,068	13,455
Cash	0	0
Loans	5,479	5,634
Total financial assets	15,340,906	15,345,596
Financial liabilities:
Obligations under investment and repurchase agreements	100,858	161,821
Liabilities for net financial guarantees written	3,044,698	4,539,000
Long-term debt	1,179,298	1,379,864
Total financial liabilities	6,637,737	7,561,738
Successor [Member] | Level 3 [Member] | Variable Interest Entity [Member]
Financial assets:
Restricted cash	0	0
Loans	12,183,061	12,371,177
Financial liabilities:
Long-term debt	2,143,532	1,263,664
Successor [Member] | Level 3 [Member] | Currency Swaps [Member] | Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	0
Successor [Member] | Interest Rate Swaps [Member] | Total Fair Value [Member]
Financial assets:
Derivative assets	89,743	106,974
Derivative assets - interest rate swaps - liability position	0
Successor [Member] | Interest Rate Swaps [Member] | Carrying Amount [Member]
Financial assets:
Derivative assets	89,743	106,974
Derivative assets - interest rate swaps - liability position	0
Successor [Member] | Interest Rate Swaps [Member] | Level 1 [Member]
Financial assets:
Derivative assets	0	0
Derivative assets - interest rate swaps - liability position	0	0
Successor [Member] | Interest Rate Swaps [Member] | Level 2 [Member]
Financial assets:
Derivative assets	23,796	106,974
Derivative assets - interest rate swaps - liability position	0	0
Successor [Member] | Interest Rate Swaps [Member] | Level 3 [Member]
Financial assets:
Derivative assets	65,947	0
Derivative assets - interest rate swaps - liability position	0	0
Successor [Member] | Municipal Bonds [Member] | Total Fair Value [Member]
Financial assets:
Fixed income securities	419,001	525,792
Successor [Member] | Municipal Bonds [Member] | Carrying Amount [Member]
Financial assets:
Fixed income securities	419,001	525,792
Successor [Member] | Municipal Bonds [Member] | Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | Municipal Bonds [Member] | Level 2 [Member]
Financial assets:
Fixed income securities	419,001	525,792
Successor [Member] | Municipal Bonds [Member] | Level 3 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | Corporate Obligations [Member] | Total Fair Value [Member]
Financial assets:
Fixed income securities	1,587,578	1,385,594
Successor [Member] | Corporate Obligations [Member] | Total Fair Value [Member] | Variable Interest Entity [Member]
Financial assets:
Fixed income securities	2,679,895	2,743,050
Successor [Member] | Corporate Obligations [Member] | Carrying Amount [Member]
Financial assets:
Fixed income securities	1,587,578	1,385,594
Successor [Member] | Corporate Obligations [Member] | Carrying Amount [Member] | Variable Interest Entity [Member]
Financial assets:
Fixed income securities	2,679,895	2,743,050
Successor [Member] | Corporate Obligations [Member] | Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | Corporate Obligations [Member] | Level 1 [Member] | Variable Interest Entity [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | Corporate Obligations [Member] | Level 2 [Member]
Financial assets:
Fixed income securities	1,587,578	1,381,786
Successor [Member] | Corporate Obligations [Member] | Level 2 [Member] | Variable Interest Entity [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | Corporate Obligations [Member] | Level 3 [Member]
Financial assets:
Fixed income securities	0	3,808
Successor [Member] | Corporate Obligations [Member] | Level 3 [Member] | Variable Interest Entity [Member]
Financial assets:
Fixed income securities	2,679,895	2,743,050
Successor [Member] | Foreign Obligations [Member] | Total Fair Value [Member]
Financial assets:
Fixed income securities	103,654	127,757
Successor [Member] | Foreign Obligations [Member] | Carrying Amount [Member]
Financial assets:
Fixed income securities	103,654	127,757
Successor [Member] | Foreign Obligations [Member] | Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | Foreign Obligations [Member] | Level 2 [Member]
Financial assets:
Fixed income securities	103,654	127,757
Successor [Member] | Foreign Obligations [Member] | Level 3 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | US Government Debt Securities [Member] | Total Fair Value [Member]
Financial assets:
Fixed income securities	30,863	42,979
Fixed income securities, pledged as collateral	64,972	64,267
Successor [Member] | US Government Debt Securities [Member] | Carrying Amount [Member]
Financial assets:
Fixed income securities	30,863	42,979
Fixed income securities, pledged as collateral	64,972	64,267
Successor [Member] | US Government Debt Securities [Member] | Level 1 [Member]
Financial assets:
Fixed income securities	30,863	42,979
Fixed income securities, pledged as collateral	64,972	64,267
Successor [Member] | US Government Debt Securities [Member] | Level 2 [Member]
Financial assets:
Fixed income securities	0	0
Fixed income securities, pledged as collateral	0	0
Successor [Member] | US Government Debt Securities [Member] | Level 3 [Member]
Financial assets:
Fixed income securities	0	0
Fixed income securities, pledged as collateral	0	0
Successor [Member] | U.S. Agency Obligations [Member] | Total Fair Value [Member]
Financial assets:
Fixed income securities	4,281	29,486
Successor [Member] | U.S. Agency Obligations [Member] | Carrying Amount [Member]
Financial assets:
Fixed income securities	4,281	29,486
Successor [Member] | U.S. Agency Obligations [Member] | Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | U.S. Agency Obligations [Member] | Level 2 [Member]
Financial assets:
Fixed income securities	4,281	29,486
Successor [Member] | U.S. Agency Obligations [Member] | Level 3 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | Residential Mortgage-Backed Securities [Member] | Total Fair Value [Member]
Financial assets:
Fixed income securities	1,871,483	1,710,955
Successor [Member] | Residential Mortgage-Backed Securities [Member] | Carrying Amount [Member]
Financial assets:
Fixed income securities	1,871,483	1,710,955
Successor [Member] | Residential Mortgage-Backed Securities [Member] | Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | Residential Mortgage-Backed Securities [Member] | Level 2 [Member]
Financial assets:
Fixed income securities	1,487,694	1,516,562
Successor [Member] | Residential Mortgage-Backed Securities [Member] | Level 3 [Member]
Financial assets:
Fixed income securities	383,789	194,393
Successor [Member] | Collateralized Debt Obligations [Member] | Total Fair Value [Member]
Financial assets:
Fixed income securities	81,912	21,122
Successor [Member] | Collateralized Debt Obligations [Member] | Carrying Amount [Member]
Financial assets:
Fixed income securities	81,912	21,122
Successor [Member] | Collateralized Debt Obligations [Member] | Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | Collateralized Debt Obligations [Member] | Level 2 [Member]
Financial assets:
Fixed income securities	81,912	21,122
Successor [Member] | Collateralized Debt Obligations [Member] | Level 3 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | Asset-backed Securities [Member] | Total Fair Value [Member]
Financial assets:
Fixed income securities	858,104	882,001
Successor [Member] | Asset-backed Securities [Member] | Carrying Amount [Member]
Financial assets:
Fixed income securities	858,104	882,001
Successor [Member] | Asset-backed Securities [Member] | Level 1 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | Asset-backed Securities [Member] | Level 2 [Member]
Financial assets:
Fixed income securities	858,104	882,001
Successor [Member] | Asset-backed Securities [Member] | Level 3 [Member]
Financial assets:
Fixed income securities	0	0
Successor [Member] | Short-Term [Member] | Total Fair Value [Member]
Financial assets:
Short term investments	364,780	360,065
Successor [Member] | Short-Term [Member] | Carrying Amount [Member]
Financial assets:
Short term investments	364,780	360,065
Successor [Member] | Short-Term [Member] | Level 1 [Member]
Financial assets:
Short term investments	305,950	358,190
Successor [Member] | Short-Term [Member] | Level 2 [Member]
Financial assets:
Short term investments	58,830	1,875
Successor [Member] | Short-Term [Member] | Level 3 [Member]
Financial assets:
Short term investments	0	0
Successor [Member] | Credit Derivatives [Member] | Total Fair Value [Member]
Financial assets:
Derivative assets	1,345	2,043
Successor [Member] | Credit Derivatives [Member] | Carrying Amount [Member]
Financial assets:
Derivative assets	1,345	2,043
Successor [Member] | Credit Derivatives [Member] | Level 1 [Member]
Financial assets:
Derivative assets	0	0
Successor [Member] | Credit Derivatives [Member] | Level 2 [Member]
Financial assets:
Derivative assets	0	0
Successor [Member] | Credit Derivatives [Member] | Level 3 [Member]
Financial assets:
Derivative assets	1,345	2,043
Successor [Member] | Other Assets [Member] | Total Fair Value [Member]
Financial assets:
Other assets	9,322	12,036
Successor [Member] | Other Assets [Member] | Carrying Amount [Member]
Financial assets:
Other assets	9,322	12,036
Successor [Member] | Other Assets [Member] | Level 1 [Member]
Financial assets:
Other assets	0	0
Successor [Member] | Other Assets [Member] | Level 2 [Member]
Financial assets:
Other assets	0	0
Successor [Member] | Other Assets [Member] | Level 3 [Member]
Financial assets:
Other assets	9,322	12,036
Successor [Member] | Futures Contracts [Member] | Total Fair Value [Member]
Financial assets:
Derivative assets		0
Successor [Member] | Futures Contracts [Member] | Carrying Amount [Member]
Financial assets:
Derivative assets		0
Successor [Member] | Futures Contracts [Member] | Level 1 [Member]
Financial assets:
Derivative assets		0
Successor [Member] | Futures Contracts [Member] | Level 2 [Member]
Financial assets:
Derivative assets		0
Successor [Member] | Futures Contracts [Member] | Level 3 [Member]
Financial assets:
Derivative assets		0
Other Contracts [Member] | Successor [Member] | Total Fair Value [Member]
Financial liabilities:
Derivative liabilities		0
Other Contracts [Member] | Successor [Member] | Carrying Amount [Member]
Financial liabilities:
Derivative liabilities		0
Other Contracts [Member] | Successor [Member] | Level 1 [Member]
Financial liabilities:
Derivative liabilities		0
Other Contracts [Member] | Successor [Member] | Level 2 [Member]
Financial liabilities:
Derivative liabilities		0
Other Contracts [Member] | Successor [Member] | Level 3 [Member]
Financial liabilities:
Derivative liabilities		0
Futures Contracts [Member] | Successor [Member] | Total Fair Value [Member]
Financial liabilities:
Derivative liabilities	220	562
Futures Contracts [Member] | Successor [Member] | Carrying Amount [Member]
Financial liabilities:
Derivative liabilities	220	562
Futures Contracts [Member] | Successor [Member] | Level 1 [Member]
Financial liabilities:
Derivative liabilities	220	562
Futures Contracts [Member] | Successor [Member] | Level 2 [Member]
Financial liabilities:
Derivative liabilities	0	0
Futures Contracts [Member] | Successor [Member] | Level 3 [Member]
Financial liabilities:
Derivative liabilities	0	0
Interest Rate Swaps [Member] | Successor [Member] | Total Fair Value [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	(63,785)	(54,666)
Derivative liabilities	408,168	385,546
Interest Rate Swaps [Member] | Successor [Member] | Total Fair Value [Member] | Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	2,065,224	2,133,268
Interest Rate Swaps [Member] | Successor [Member] | Carrying Amount [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	(63,785)	(54,666)
Derivative liabilities	408,168	385,546
Interest Rate Swaps [Member] | Successor [Member] | Carrying Amount [Member] | Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	2,065,224	2,133,268
Interest Rate Swaps [Member] | Successor [Member] | Level 1 [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	0	0
Derivative liabilities	0	0
Interest Rate Swaps [Member] | Successor [Member] | Level 1 [Member] | Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	0	0
Interest Rate Swaps [Member] | Successor [Member] | Level 2 [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	(63,785)	(54,666)
Derivative liabilities	270,049	243,659
Interest Rate Swaps [Member] | Successor [Member] | Level 2 [Member] | Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	2,065,224	2,133,268
Interest Rate Swaps [Member] | Successor [Member] | Level 3 [Member]
Financial liabilities:
Derivative liabilities - interest rate swaps - asset position	0	0
Derivative liabilities	138,119	141,887
Interest Rate Swaps [Member] | Successor [Member] | Level 3 [Member] | Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	0	0
Credit Derivatives [Member] | Successor [Member] | Total Fair Value [Member]
Financial liabilities:
Derivative liabilities	31,232	75,502
Credit Derivatives [Member] | Successor [Member] | Carrying Amount [Member]
Financial liabilities:
Derivative liabilities	31,232	75,502
Credit Derivatives [Member] | Successor [Member] | Level 1 [Member]
Financial liabilities:
Derivative liabilities	0	0
Credit Derivatives [Member] | Successor [Member] | Level 2 [Member]
Financial liabilities:
Derivative liabilities	0	0
Credit Derivatives [Member] | Successor [Member] | Level 3 [Member]
Financial liabilities:
Derivative liabilities	31,232	75,502
Currency Swaps [Member] | Successor [Member] | Total Fair Value [Member] | Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	(31,429)	66,895
Currency Swaps [Member] | Successor [Member] | Carrying Amount [Member] | Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	(31,429)	66,895
Currency Swaps [Member] | Successor [Member] | Level 1 [Member] | Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	0	0
Currency Swaps [Member] | Successor [Member] | Level 2 [Member] | Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities	$ (31,429)	66,895
Currency Swaps [Member] | Successor [Member] | Level 3 [Member] | Variable Interest Entity [Member]
Financial liabilities:
Derivative liabilities		$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2014
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Credit valuation adjustment included in fair value of credit derivative liabilities	$ 8,497	$ 8,497	$ 15,910
Credit valuation adjustment included in fair value of derivative liabilities other than credit derivatives	$ 83,983	$ 83,983	64,547
Percentage of CDS gross par outstanding used in the determination of CDS fair values	85.00%	85.00%
Percentage of CDS derivative liability used in the determination of CDS fair values	49.00%	49.00%
Percentage of CDS gross par outstanding using internally estimated reference obligation prices in determination of fair value	15.00%	15.00%
Percentage of CDS liability using internally estimated reference obligation prices in determination of fair value	51.00%	51.00%
Additional basis point fee need to receive for issuing a CDS on obligation	0.05%
Additional basis points fee increase on change of reference obligation spread	0.15%
Revised relative change ratio of CDS fee to cash market spread	73.20%
Estimated remaining life	8 years
Notional outstanding	$ 1,313,797	$ 1,313,797	1,529,759
Derivative liabilities	$ 29,887	$ 29,887	$ 73,459
Credit Derivatives [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
CVA percentage	21.40%	21.40%	17.80%
US Commercial ABS Transaction [Member] | Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair value of consolidated VIE debt obligations valued using unobservable inputs by asset class	$ 165,269	$ 165,269
Minimum [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Basis point fee received for issuing a CDS on reference obligation base fee	0.20%
Credit spread of reference obligation of a base transaction	0.80%	0.80%
Relative change ratio of CDS fee to cash market spread	25.00%
Maximum [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Basis point fee received for issuing a CDS on reference obligation hypothetical fee	0.25%
Relative change ratio of CDS fee to cash market spread	35.00%
Credit spread of reference obligation of revised transaction	1.00%	1.00%
Internal Credit Rating [Member] | Minimum [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Revised relative change ratio of CDS fee to cash market spread	33.00%
Internal Credit Rating [Member] | Maximum [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Full relative change ratio of CDS fee to cash market spread	100.00%
Successor [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Weighted average discounted rate of estimated future premium payments to be paid by the VIEs	2.70%	2.70%	2.70%
Available-for-sale Securities	$ 5,386,628	$ 5,386,628	$ 5,150,018
Successor [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Percentage of investment portfolio valued using dealer quotes	9.00%	9.00%	10.00%
Percentage of investment portfolio valued using external pricing services	84.00%	84.00%	86.00%
Percentage of investment portfolio valued using internal valuation models	7.00%	7.00%	4.00%
Successor [Member] | U.S. Agency Obligations [Member] | Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sale Securities	$ 0	$ 0	$ 0
Successor [Member] | Asset-backed Securities [Member] | Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sale Securities	0	0	0
Successor [Member] | Residential Mortgage-Backed Securities [Member] | Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sale Securities	$ 383,789	$ 383,789	194,393
Successor [Member] | Corporate Obligations [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Coupon rate	0.345%	0.345%
Fair Value Inputs Maturity		19 years 1 month 21 days
Fair Value Inputs Yield	4.93%	4.93%
Successor [Member] | Corporate Obligations [Member] | Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sale Securities	$ 0	$ 0	3,808
Successor [Member] | Collateralized Debt Obligations [Member] | Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sale Securities	0	0	0
Successor [Member] | European ABS Transactions [Member] | Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair value of consolidated VIE debt obligations valued using unobservable inputs by asset class	$ 1,978,263	$ 1,978,263	1,070,439
Successor [Member] | US Commercial ABS Transaction [Member] | Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair value of consolidated VIE debt obligations valued using unobservable inputs by asset class			$ 193,225
Variable Interest Entities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Weighted average discounted rate of estimated future premium payments to be paid by the VIEs	3.90%	3.90%	4.10%
Other Contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fair Value Input Weighted Average Credit Derivative Quote As Percentage Of Notional	1.00%	1.00%	1.00%
Fair Value Input Weighted Average Credit Rating	A+		A
CVA percentage	1.09%	1.09%	2.21%
Notional outstanding	$ 58,482	$ 58,482	$ 58,800
Fair Value Input Weighted Average Life	4 months 24 days		1 year 2 months 12 days
Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member] | Corporate Obligations [Member] | Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Available-for-sale Securities	$ 2,679,895	$ 2,679,895	$ 2,743,050
Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member] | European ABS Transactions [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Coupon rate	0.54%	0.54%	0.30%
Fair Value Inputs Maturity		17 years 5 months 5 days	21 years 2 months 30 days
Fair Value Inputs Yield	7.46%	7.46%	9.52%
Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member] | US Commercial ABS Transaction [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Coupon rate	5.88%	5.88%	5.88%
Fair Value Inputs Maturity		22 years 23 days	16 years 4 months 18 days
Fair Value Inputs Yield	9.00%	9.00%	7.77%

Fair Value Measurements - Infor

Fair Value Measurements - Information about Valuation Inputs for Fixed Income Securities Classified as Level 3 (Detail) - Successor [Member]	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Corporate Obligations [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Coupon rate	0.345%
Fair Value Inputs Maturity	19 years 1 month 21 days
Yield	4.93%
Variable Interest Entity, Primary Beneficiary [Member] | United States Transactions [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Coupon rate	5.88%	5.88%
Fair Value Inputs Maturity	22 years 23 days	16 years 4 months 18 days
Yield	9.00%	7.77%
Variable Interest Entity, Primary Beneficiary [Member] | European Transactions [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Coupon rate	0.54%	0.30%
Fair Value Inputs Maturity	17 years 5 months 5 days	21 years 2 months 30 days
Yield	7.46%	9.52%

Fair Value Measurements - Sum57

Fair Value Measurements - Summary of Information about Described Model Inputs Used to Determine Fair Value of Each Class of Credit Derivatives (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Notional outstanding	$ 1,313,797	$ 1,529,759
Successor [Member] | CLO [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Notional outstanding	$ 341,668	$ 549,923
Weighted average reference obligation price	$ 98.5	$ 98.9
Weighted average life (WAL) in years	1 year	1 year 9 months
Weighted average credit rating	AA	AA
Weighted average relative change ratio	36.30%	35.90%
CVA percentage	7.48%	5.40%
Fair value of derivative liabilities	$ 1,740	$ 2,027
Successor [Member] | Other [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Notional outstanding	$ 913,647	$ 921,036
Weighted average reference obligation price	$ 85.9	$ 86.8
Weighted average life (WAL) in years	4 years 2 months 12 days	5 years 8 months
Weighted average credit rating	BBB-	BBB-
Weighted average relative change ratio	45.30%	49.00%
CVA percentage	22.91%	15.82%
Fair value of derivative liabilities	$ 28,125	$ 71,104

Fair Value Measurements - Sum58

Fair Value Measurements - Summary of Information about Described Model Inputs Used to Determine Fair Value of Each Class of Credit Derivatives (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Notional outstanding	$ 1,313,797	$ 1,529,759
Other Contracts [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Notional outstanding	$ 58,482	$ 58,800
Weighted average life (WAL) in years	4 months 24 days	1 year 2 months 12 days
Weighted average quotes	1.00%	1.00%
CVA percentage	1.09%	2.21%
Weighted average credit rating	A+	A
Fair value of derivative liabilities	$ 22	$ 328

Fair Value Measurements - Inf59

Fair Value Measurements - Information about Valuation Inputs for Variable Interest Entity Assets and Liabilities Classified as Level 3 (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Inputs, Level 3 [Member] | US Commercial ABS Transaction [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Of Consolidated Variable Interest Entity Debt Obligations Valued Using Unobservable Inputs By Asset Class	$ 165,269		$ 165,269
Fair Value, Inputs, Level 3 [Member] | Successor [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	13,010,477	$ 13,725,623	13,010,477	$ 13,725,623	$ 13,856,298	$ 13,845,454	$ 14,917,043	$ 14,253,705
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings	52,394	301,522	(166,100)	666,194
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	(503,211)	(758,705)	(402,726)	(305,933)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	28	0	234,880	70,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	3,388	0	3,388
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	69,909	70,951	264,126	294,849
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	88,218	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three		659,898		660,106
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Deconsolidation Of Vies	325,123		325,123
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	22,297	307,213	(217,197)	666,198
Fair Value, Inputs, Level 3 [Member] | Successor [Member] | Investments [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	383,789	62,660	383,789	62,660	380,332	198,201	66,352	67,783
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings	8,429	835	21,066	1,676
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	(4,288)	(254)	(48,611)	(595)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	28	0	234,880	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	3,388	0	3,388
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	712	885	21,747	2,608
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three	0	0	0	208
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Deconsolidation Of Vies	0		0
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	0	0	0	0
Fair Value, Inputs, Level 3 [Member] | Successor [Member] | European ABS Transactions [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Of Consolidated Variable Interest Entity Debt Obligations Valued Using Unobservable Inputs By Asset Class	1,978,263		1,978,263			1,070,439
Fair Value, Inputs, Level 3 [Member] | Successor [Member] | US Commercial ABS Transaction [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Of Consolidated Variable Interest Entity Debt Obligations Valued Using Unobservable Inputs By Asset Class						193,225
Fair Value, Inputs, Level 3 [Member] | Successor [Member] | Other Assets [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	9,322	12,401	9,322	12,401	9,704	12,036	12,782	13,384
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings	(382)	(381)	(1,009)	(983)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	0	0	1,705	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Deconsolidation Of Vies			0
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	(382)	(381)	(1,009)	(983)
Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Successor [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	(102,058)	(215,902)	(102,058)	(215,902)	(119,309)	(215,346)	(218,661)	(186,934)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings	20,073	3,885	20,640	(36,323)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	2,822	1,126	(4,430)	(7,355)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	88,218	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Deconsolidation Of Vies	0		0
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	(12,285)	3,229	(20,081)	(39,830)
Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			(196,107)	707,011
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Inputs, Level 3 [Member] | Successor [Member] | Loans Receivable [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	12,183,061	12,503,484	12,183,061	12,503,484	13,005,216	12,371,177	13,743,231	13,398,895
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings	44,404	209,028	701,562	735,597
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	(471,321)	(678,944)	(311,773)	(270,727)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	70,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	70,115	73,042	252,782	733,492
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three		696,789		696,789
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Deconsolidation Of Vies	325,123		325,123
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	102,901	215,296	760,059	736,732
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Inputs, Level 3 [Member] | Successor [Member] | Corporate Debt Securities [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	2,679,895	2,651,683	2,679,895	2,651,683	2,747,181	2,743,050	2,688,388	2,475,182
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings	39,630	105,116	14,490	235,178
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	(106,916)	(141,821)	(77,645)	(58,677)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Deconsolidation Of Vies	0		0
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	39,630	105,116	14,490	235,178
Variable Interest Entity, Primary Beneficiary [Member] | Long-term Debt [Member] | Fair Value, Inputs, Level 3 [Member] | Successor [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	(2,143,532)	(1,288,703)	(2,143,532)	(1,288,703)	$ (2,166,826)	$ (1,263,664)	$ (1,375,049)	$ (1,514,605)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings	(59,760)	(16,961)	(922,849)	(268,951)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	79,314	62,314	35,303	24,066
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(3,740)	(4,102)	(7,678)	(433,896)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three		(36,891)	0	(36,891)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Deconsolidation Of Vies	0		0
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	$ (107,567)	$ (16,047)	$ (970,656)	$ (264,899)

Fair Value Measurements - Sum60

Fair Value Measurements - Summary of Changes in Level 3 Fair Value Category (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Investment by Class [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 380,332	$ 66,352	$ 198,201	$ 67,783
Additions of VIEs consolidated			0	0
Included in earnings	8,429	835	21,066	1,676
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	(4,288)	(254)	(48,611)	(595)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	28		234,880
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales		(3,388)		(3,388)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(712)	(885)	(21,747)	(2,608)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three				(208)
Balance, end of period	383,789	62,660	383,789	62,660
Derivatives by Class [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	(119,309)	(218,661)	(215,346)	(186,934)
Included in earnings	20,073	3,885	20,640	(36,323)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(2,822)	(1,126)	4,430	7,355
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	88,218	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three	0	0	0	0
Balance, end of period	(102,058)	(215,902)	(102,058)	(215,902)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	12,285	(3,229)	20,081	39,830
Credit Derivative [Member] | Derivatives by Class [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	(66,490)	(89,651)	(73,459)	(94,322)
Included in earnings	36,952	7,417	44,746	13,580
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(349)	(596)	(1,174)	(2,088)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three	0	0	0	0
Balance, end of period	(29,887)	(82,830)	(29,887)	(82,830)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	(4,594)	(6,761)	(4,025)	(10,073)
Interest Rate Swaps [Member] | Derivatives by Class [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	(52,819)	(129,010)	(141,887)	(92,612)
Included in earnings	(16,879)	(3,532)	(24,106)	(49,903)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(2,473)	(530)	5,604	9,443
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	88,218	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three	0	0	0	0
Balance, end of period	(72,171)	(133,072)	(72,171)	(133,072)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	16,879	3,532	24,106	49,903
Residential Mortgage-Backed Securities [Member] | Investment by Class [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	380,332	0	194,393	0
Additions of VIEs consolidated			0	0
Included in earnings	8,429	0	21,085	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	(4,288)		(48,325)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	28		234,880
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(712)	0	(18,244)	0
Balance, end of period	383,789		383,789
Asset-backed Securities [Member] | Investment by Class [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	62,601	0	64,073
Additions of VIEs consolidated			0	0
Included in earnings	0	859	0	1,748
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	0	(272)	0	(910)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales		(3,388)		(3,388)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	0	(885)	0	(2,608)
Balance, end of period	0	58,915	0	58,915
Corporate Obligations [Member] | Investment by Class [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	3,751	3,808	3,502
Additions of VIEs consolidated			0	0
Included in earnings	0	(24)	(19)	(72)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	0	18	(286)	315
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements			(3,503)
Balance, end of period	0	3,745	0	3,745
US Government Agencies Debt Securities [Member] | Investment by Class [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	0	0	0	208
Additions of VIEs consolidated			0	0
Included in earnings	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three				(208)
Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	13,856,298	14,917,043	13,845,454	14,253,705
Included in earnings	52,394	301,522	(166,100)	666,194
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	(503,211)	(758,705)	(402,726)	(305,933)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	28	0	234,880	70,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	3,388	0	3,388
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	69,909	70,951	264,126	294,849
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	88,218	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three		659,898		660,106
Deconsolidation of VIEs	325,123		325,123
Balance, end of period	13,010,477	13,725,623	13,010,477	13,725,623
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	(22,297)	(307,213)	217,197	(666,198)
Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	(119,309)	(218,661)	(215,346)	(186,934)
Included in earnings	20,073	3,885	20,640	(36,323)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	2,822	1,126	(4,430)	(7,355)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	88,218	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three	0	0	0	0
Deconsolidation of VIEs	0		0
Balance, end of period	(102,058)	(215,902)	(102,058)	(215,902)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	12,285	(3,229)	20,081	39,830
Level 3 [Member] | Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	380,332	66,352	198,201	67,783
Included in earnings	8,429	835	21,066	1,676
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	(4,288)	(254)	(48,611)	(595)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	28	0	234,880	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	3,388	0	3,388
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	712	885	21,747	2,608
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three	0	0	0	208
Deconsolidation of VIEs	0		0
Balance, end of period	383,789	62,660	383,789	62,660
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	0	0	0	0
Level 3 [Member] | Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	9,704	12,782	12,036	13,384
Included in earnings	(382)	(381)	(1,009)	(983)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	0	0	1,705	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three	0	0	0	0
Deconsolidation of VIEs			0
Balance, end of period	9,322	12,401	9,322	12,401
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	382	381	1,009	983
Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date			196,107	(707,011)
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member] | Long-Term Debt [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	(2,166,826)	(1,375,049)	(1,263,664)	(1,514,605)
Included in earnings	(59,760)	(16,961)	(922,849)	(268,951)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	79,314	62,314	35,303	24,066
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(3,740)	(4,102)	(7,678)	(433,896)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three		(36,891)	0	(36,891)
Deconsolidation of VIEs	0		0
Balance, end of period	(2,143,532)	(1,288,703)	(2,143,532)	(1,288,703)
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	107,567	16,047	970,656	264,899
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member] | Loans Receivable [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	13,005,216	13,743,231	12,371,177	13,398,895
Included in earnings	44,404	209,028	701,562	735,597
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	(471,321)	(678,944)	(311,773)	(270,727)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	70,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	70,115	73,042	252,782	733,492
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three		696,789		696,789
Deconsolidation of VIEs	325,123		325,123
Balance, end of period	12,183,061	12,503,484	12,183,061	12,503,484
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	(102,901)	(215,296)	(760,059)	(736,732)
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member] | Corporate Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	2,747,181	2,688,388	2,743,050	2,475,182
Included in earnings	39,630	105,116	14,490	235,178
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	(106,916)	(141,821)	(77,645)	(58,677)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Issues	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Sales	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Into Level Three	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Transfers Out Of Level Three	0	0	0	0
Deconsolidation of VIEs	0		0
Balance, end of period	2,679,895	2,651,683	2,679,895	2,651,683
The amount of total gains/(losses) included in earnings attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date	$ (39,630)	$ (105,116)	$ (14,490)	$ (235,178)

Fair Value Measurements - Sum61

Fair Value Measurements - Summary of Gains and Losses (Realized and Unrealized) Relating to Level 3 Assets and Liabilities Included in Earnings (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Variable Interest Entity [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period			$ (206,797)	$ 701,824
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			(196,107)	707,011
Net Investment Income [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	$ 8,429	$ 835	21,066	1,676
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	0	0	0	0
Realized Gains Or (Losses) and Other Settlements On Credit Derivative Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	1,693	596	2,519	2,088
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	0	0	0	0
Unrealized Gains Or (Losses) On Credit Derivative Contracts [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	35,259	6,820	42,227	11,491
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	4,594	6,761	4,025	10,074
Interest Rate Swaps [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	(16,879)	(3,532)	(24,106)	(49,903)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	(16,879)	(3,532)	(24,106)	(49,903)
Income Loss On Variable Interest Entities [Member] | Variable Interest Entity [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	24,274	297,183
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	34,964	304,365
Other Income or (Loss) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	(382)	(381)	(1,009)	(983)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	$ (382)	$ (381)	$ (1,009)	$ (983)

Investments - Summary of Amorti

Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments (Detail) - Successor [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 5,298,840	$ 4,939,325
Gross Unrealized Gains	158,969	242,962
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71,181	32,269
Estimated Fair Value	5,386,628	5,150,018
Non - credit other - than - temporary Impairments	27,439	7,773
Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Estimated Fair Value	2,679,895	2,743,050
Short-Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	364,784	360,069
Gross Unrealized Gains	0	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	4	4
Estimated Fair Value	364,780	360,065
Non - credit other - than - temporary Impairments	0	0
Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,869,500	4,514,878
Gross Unrealized Gains	158,553	242,962
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71,177	32,154
Estimated Fair Value	4,956,876	4,725,686
Non - credit other - than - temporary Impairments	27,439	7,773
Fixed Income Securities [Member] | Securities Pledged as Collateral [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	64,556	64,378
Gross Unrealized Gains	416	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	111
Estimated Fair Value	64,972	64,267
Non - credit other - than - temporary Impairments	0	0
Fixed Income Securities [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	420,465	523,019
Gross Unrealized Gains	5,217	9,769
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	6,681	6,996
Estimated Fair Value	419,001	525,792
Non - credit other - than - temporary Impairments	0	0
Fixed Income Securities [Member] | Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,593,457	1,382,195
Gross Unrealized Gains	11,739	12,815
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	17,618	9,416
Estimated Fair Value	1,587,578	1,385,594
Non - credit other - than - temporary Impairments	0	0
Fixed Income Securities [Member] | Foreign Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	104,226	126,041
Gross Unrealized Gains	1,710	3,060
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	2,282	1,344
Estimated Fair Value	103,654	127,757
Non - credit other - than - temporary Impairments	0	0
Fixed Income Securities [Member] | U.S. Government Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	30,410	42,328
Gross Unrealized Gains	672	1,078
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	219	427
Estimated Fair Value	30,863	42,979
Non - credit other - than - temporary Impairments	0	0
Fixed Income Securities [Member] | U.S. Government Obligations [Member] | Securities Pledged as Collateral [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	64,556	64,378
Gross Unrealized Gains	416	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	111
Estimated Fair Value	64,972	64,267
Non - credit other - than - temporary Impairments	0	0
Fixed Income Securities [Member] | U.S. Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,283	29,524
Gross Unrealized Gains	0	0
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	2	38
Estimated Fair Value	4,281	29,486
Non - credit other - than - temporary Impairments	0	0
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,797,616	1,557,059
Gross Unrealized Gains	116,052	167,396
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	42,185	13,500
Estimated Fair Value	1,871,483	1,710,955
Non - credit other - than - temporary Impairments	27,439	7,773
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	82,734	21,346
Gross Unrealized Gains	54	50
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	876	274
Estimated Fair Value	81,912	21,122
Non - credit other - than - temporary Impairments	0	0
Fixed Income Securities [Member] | Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	836,309	833,366
Gross Unrealized Gains	23,109	48,794
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1,314	159
Estimated Fair Value	858,104	882,001
Non - credit other - than - temporary Impairments	0	0
Fixed Income Investments And Other Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,234,284	4,874,947
Gross Unrealized Gains	158,553	242,962
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71,181	32,158
Estimated Fair Value	5,321,656	5,085,751
Non - credit other - than - temporary Impairments	$ 27,439	$ 7,773

Investments - Summary of Amor63

Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments Held by Successor Ambac, by Contractual Maturity (Detail) - Successor [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Due in one year or less	$ 534,324
Amortized Cost, Due after one year through five years	900,319
Amortized Cost, Due after five years through ten years	967,158
Amortized Cost, Due after ten years	180,380
Amortized Cost, Total	2,582,181
Amortized Cost	5,298,840	$ 4,939,325
Estimated Fair Value, Due in one year or less	534,445
Estimated Fair Value, Due after one year through five years	899,172
Estimated Fair Value, Due after five years through ten years	961,706
Estimated Fair Value, Due after ten years	179,806
Estimated Fair Value due, Total	2,575,129
Fixed income securities	5,386,628	5,150,018
Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,869,500	4,514,878
Fixed income securities	4,956,876	4,725,686
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,797,616	1,557,059
Fixed income securities	1,871,483	1,710,955
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	82,734	21,346
Fixed income securities	81,912	21,122
Fixed Income Securities [Member] | Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	836,309	833,366
Fixed income securities	$ 858,104	$ 882,001

Investments - Summary of Gross

Investments - Summary of Gross Unrealized Losses and Fair Values of Ambac's Available-for-Sale Investments (Detail) - Successor [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	$ 1,954,118	$ 1,324,489
Less than 12 Months, Gross Unrealized Loss	58,351	20,081
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	341,210	350,655
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	12,830	12,188
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,295,328	1,675,144
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71,181	32,269
Short-Term [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	18,822	8,803
Less than 12 Months, Gross Unrealized Loss	4	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	18,822	8,803
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	4	4
Fixed Income Investments And Other Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	1,954,118	1,260,222
Less than 12 Months, Gross Unrealized Loss	58,351	19,970
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	341,210	350,655
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	12,830	12,188
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,295,328	1,610,877
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71,181	32,158
Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	1,935,296	1,251,419
Less than 12 Months, Gross Unrealized Loss	58,347	19,966
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	341,210	350,655
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	12,830	12,188
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	2,276,506	1,602,074
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71,177	32,154
Fixed Income Securities [Member] | Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	91,214	77,788
Less than 12 Months, Gross Unrealized Loss	1,751	1,244
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	124,358	135,076
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	4,930	5,752
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	215,572	212,864
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	6,681	6,996
Fixed Income Securities [Member] | Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	677,529	453,504
Less than 12 Months, Gross Unrealized Loss	15,731	4,998
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	104,242	172,045
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	1,887	4,418
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	781,771	625,549
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	17,618	9,416
Fixed Income Securities [Member] | Foreign Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	33,646	20,827
Less than 12 Months, Gross Unrealized Loss	1,389	748
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	7,842	14,277
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	893	596
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	41,488	35,104
Fixed Income Securities [Member] | U.S. Government Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	4,671	7,223
Less than 12 Months, Gross Unrealized Loss	150	154
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	10,789	14,735
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	69	273
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	15,460	21,958
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	219	427
Fixed Income Securities [Member] | U.S. Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	0	25,039
Less than 12 Months, Gross Unrealized Loss	0	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,281	4,378
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	2	36
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	4,281	29,417
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	2	38
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	626,063	413,203
Less than 12 Months, Gross Unrealized Loss	37,165	12,391
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	73,204	10,076
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	5,020	1,109
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	699,267	423,279
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	42,185	13,500
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	73,563	5,012
Less than 12 Months, Gross Unrealized Loss	876	274
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	73,563	5,012
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	876	274
Fixed Income Securities [Member] | Other Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	428,610	248,823
Less than 12 Months, Gross Unrealized Loss	1,285	155
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	16,494	68
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	29	4
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	445,104	248,891
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	1,314	159
Fixed Income Securities [Member] | Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	2,282	1,344
Securities Pledged as Collateral [Member] | Fixed Income Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	0	64,267
Less than 12 Months, Gross Unrealized Loss	0	111
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	0	0
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	0	64,267
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	111
Securities Pledged as Collateral [Member] | Fixed Income Securities [Member] | U.S. Government Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months, Fair Value	0	64,267
Less than 12 Months, Gross Unrealized Loss	0	111
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Accumulated In Investments	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	0	64,267
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	0	111
Securities Pledged as Collateral [Member] | Securities Pledged as Collateral [Member] | U.S. Government Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 0

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Investment [Line Items]
Payment of permitted policy claim (percent)					25.00%
Future payment of permitted policy claim (percent)					45.00%
Securities fair value	$ 6,831		$ 6,831		$ 6,790
Fair Value of Securities Placed in Trust	403,106		403,106
Successor [Member]
Investment [Line Items]
Unrealized losses on securities	58,351		58,351		20,081
Other investments	(1,424)	$ 700	10,702	$ 5,905
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	71,181		71,181		32,269
Below Investment Grade Securities and Non-Rated Securities [Member] | Successor [Member]
Investment [Line Items]
Fair value of below investment grade securities and non-rated securities	788,174		788,174		473,656
Gross unrealized loss	44,497		44,497		16,001
Ambac Wrapped Securities [Member]
Investment [Line Items]
Available For Sale Securities Gross Unrealized Loss Accumulated In Investments	40,877		40,877
Gains (losses) on securities held as of reporting date [Member] | Successor [Member]
Investment [Line Items]
Other investments	(3,482)	$ 329	(41)	$ 5,965
Ambac UK [Member]
Investment [Line Items]
Asset Backed Securities Fair Value Disclosure	78,925		$ 78,925		51,395
National Century Financial Enterprises, Inc. [Member]
Investment [Line Items]
Cash recoveries	$ 0				$ 35

Investments - Summary of Amount

Investments - Summary of Amounts Included in Net Realized (Losses) Gains and Other-Than-Temporary Impairments (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Investment [Line Items]
Gross realized gains on securities	$ 343	$ 7,658	$ 54,484	$ 37,355
Gross realized losses on securities	(2,463)	(3,908)	(7,431)	(7,779)
Foreign exchange (losses) gains	4,226	6,295	3,801	(175)
Net realized (losses) gains	2,106	10,045	50,854	29,401
Net other-than-temporary impairments	$ (9,150)	$ (5,011)	$ (13,289)	$ (24,157)

Investments - Summary of Roll-F

Investments - Summary of Roll-Forward of Ambac's Cumulative Credit Losses on Debt Securities for Which Portion of Other-than-Temporary Impairment was Recognized in Other Comprehensive Income (Detail) - Successor [Member] - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance at beginning		$ 12,519	$ 14,062	$ 1,182
Additions for credit impairments recognized on:
Securities not previously impaired	$ 7,172	11,337
Securities previously impaired	4,059
Reductions for credit impairments previously recognized on:
Securities that matured or were sold during the period	$ 0	0
Balance at end		$ 12,519	$ 14,062	$ 1,182

Investments - Summary of Source

Investments - Summary of Sources of Collateral Received and Various Investment Agreement in which Collateral Pledged (Detail) - Successor [Member] - Cash and Securities Pledged Directly from Investment Portfolio [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investment [Line Items]
Fair Value of Cash and Underlying Securities	$ 348,584	$ 379,423
Fair Value of Cash and Securities Pledged to Investment and Repurchase Agreement Counterparties	108,398	156,916
Fair Value of Cash and Securities Pledged to Derivative Counterparties	$ 240,186	$ 222,507

Investments - Summary of Fair V

Investments - Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities (Detail) - Successor [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Standard & Poor's, CCC- Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	$ 2,172,102	$ 2,199,719
Standard & Poor's, A Rating [Member] | Assured Guaranty Municipal Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		119,492
Standard & Poor's, A- Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	48,695	67,895
Standard & Poor's, A+ Rating [Member] | Assured Guaranty Municipal Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	58,794
Standard & Poor's, A+ Rating [Member] | MBIA Insurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	29,108	32,460
Standard & Poor's, CCC Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	2,308,699	2,419,566
Municipal Bonds [Member] | Standard & Poor's, CCC- Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	53,097	53,164
Municipal Bonds [Member] | Standard & Poor's, A Rating [Member] | Assured Guaranty Municipal Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		119,492
Municipal Bonds [Member] | Standard & Poor's, A- Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	48,695	67,895
Municipal Bonds [Member] | Standard & Poor's, A+ Rating [Member] | Assured Guaranty Municipal Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	58,794
Municipal Bonds [Member] | Standard & Poor's, CCC Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	160,586	240,551
Corporate Debt Securities [Member] | Standard & Poor's, A Rating [Member] | Assured Guaranty Municipal Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		0
Corporate Debt Securities [Member] | Standard & Poor's, A- Rating [Member] | National Public Finance Guarantee Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	0	0
Corporate Debt Securities [Member] | Standard & Poor's, A+ Rating [Member] | Assured Guaranty Municipal Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	0
Corporate Debt Securities [Member] | Standard & Poor's, A+ Rating [Member] | MBIA Insurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	29,108	32,460
Corporate Debt Securities [Member] | Standard & Poor's, CCC Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	29,108	32,460
Mortgage and Asset-Backed Securities [Member] | Standard & Poor's, CCC- Rating [Member] | Ambac Assurance Corporation [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	2,119,005	2,146,555
Mortgage and Asset-Backed Securities [Member] | Standard & Poor's, CCC Rating [Member]
Investment [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	$ 2,119,005	$ 2,146,555

Investments - Summary of Fair70

Investments - Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Ambac UK [Member]
Investment [Line Items]
Asset Backed Securities Fair Value Disclosure	$ 78,925	$ 51,395

Investments - Summary of Net In

Investments - Summary of Net Investment Income (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Investment [Line Items]
Fixed income securities	$ 67,293	$ 84,339	$ 197,506	$ 233,878
Short-term investments	85	832	186	2,000
Loans	113	123	338	415
Investment expense	(1,872)	(2,413)	(6,801)	(7,723)
Securities available-for-sale and short-term	65,619	82,881	191,229	228,570
Other investments	(1,424)	700	10,702	5,905
Total net investment income	64,195	83,581	201,931	234,475
Gains (losses) on securities held as of reporting date [Member]
Investment [Line Items]
Net Realized and Unrealized Gain (Loss) on Trading Securities	(2,549)	329	7,493	5,534
Trading Securities, Realized Gain (Loss)	933	0	7,534	(431)
Other investments	$ (3,482)	$ 329	$ (41)	$ 5,965

Derivative Instruments - Summar

Derivative Instruments - Summary of Gross Fair Values of Individual Derivative Instruments (Detail) - Successor [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	$ 154,873	$ 163,683
Gross Amounts of Recognized Liabilities, Derivative Liabilities	439,620	461,610
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	63,785	54,666
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	63,785	54,666
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	91,088	109,017
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	375,835	406,944
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Assets	0	0
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	186,752	170,135
Net Amount, Derivative Assets	91,088	109,017
Net Amount, Derivative Liabilities	189,083	236,809
Variable Interest Entities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	31,429
Gross Amounts of Recognized Liabilities, Derivative Liabilities	2,065,224	2,200,163
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	31,429	0
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	31,429	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	2,033,795	2,200,163
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Assets	0
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	0	0
Net Amount, Derivative Assets	0
Net Amount, Derivative Liabilities	2,033,795	2,200,163
Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	153,528	161,640
Gross Amounts of Recognized Liabilities, Derivative Liabilities	408,168	385,546
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	63,785	54,666
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	63,785	54,666
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	89,743	106,974
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	344,383	330,880
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	186,752	169,573
Net Amount, Derivative Assets	89,743	106,974
Net Amount, Derivative Liabilities	157,631	161,307
Interest Rate Swaps [Member] | Variable Interest Entities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	0
Gross Amounts of Recognized Liabilities, Derivative Liabilities	2,065,224	2,133,268
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	2,065,224	2,133,268
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Assets	0
Net Amount, Derivative Assets	0
Net Amount, Derivative Liabilities	2,065,224	2,133,268
Futures Contracts [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Liabilities, Derivative Liabilities	220	562
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	220	562
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities	0	562
Net Amount, Derivative Liabilities	220
Credit Derivatives [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	1,345	2,043
Gross Amounts of Recognized Liabilities, Derivative Liabilities	31,232	75,502
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0	0
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	0	0
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	1,345	2,043
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	31,232	75,502
Net Amount, Derivative Assets	1,345	2,043
Net Amount, Derivative Liabilities	31,232	75,502
Currency Swaps [Member] | Variable Interest Entities [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets, Derivative Assets	31,429
Gross Amounts of Recognized Liabilities, Derivative Liabilities	0	66,895
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	31,429
Gross Amounts Offset in the Consolidated Balance Sheet, Derivative Assets / Liabilities	31,429
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	(31,429)	66,895
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Assets	0
Net Amount, Derivative Assets	0
Net Amount, Derivative Liabilities	$ (31,429)	$ 66,895

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Detail)	Sep. 30, 2015USD ($)Contract	Dec. 31, 2014USD ($)Contract
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Value of right to reclaim cash collateral and posted margin, recorded in "Other assets"	$ 175,214,000	$ 158,240,000
Value of obligation to return cash collateral, recorded in "Other liabilities"	0	0
Net liability fair value of all derivative instruments linked to Ambac's own credit risk	101,698,000	92,869,000
Fair value of posted assets as collateral	$ 153,901,000	$ 118,844,000
Credit Derivatives [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Number of credit derivative contracts | Contract	4	4
Net liability fair value of credit derivative contracts	$ 14,958,000	$ 60,729,000
Notional value of credit derivative contracts	$ 259,852,000	$ 270,747,000

Derivative Instruments - Summ74

Derivative Instruments - Summary of Location and Amount of Gains and Losses of Derivative Contracts (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	$ (31,689)	$ (36,101)	$ 114,484	$ (286,918)
Net Change in Fair Value of Credit Derivatives [Member] | Credit Derivatives [Member] | Financial Guarantee [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	36,952	7,416	44,746	13,579
Derivative Products [Member] | Financial Services Derivatives Products [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	(65,083)	(15,685)	(51,858)	(117,511)
Derivative Products [Member] | Interest Rate Swaps [Member] | Financial Services Derivatives Products [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	(63,044)	(15,638)	(48,839)	(112,995)
Derivative Products [Member] | Futures Contracts [Member] | Financial Services Derivatives Products [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	(2,039)	(47)	(3,019)	(4,516)
Income Loss On Variable Interest Entities [Member] | Variable Interest Entity [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	(3,558)	(27,832)	121,596	(182,986)
Income Loss On Variable Interest Entities [Member] | Interest Rate Swaps [Member] | Variable Interest Entity [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	(15,793)	(44,846)	68,044	(204,411)
Income Loss On Variable Interest Entities [Member] | Currency Swaps [Member] | Variable Interest Entity [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Derivative instruments, gain (loss) recognized in income, net, Total	$ 12,235	$ 17,014	$ 53,552	$ 21,425

Derivative Instruments - Summ75

Derivative Instruments - Summary of Gross Principal Notional Outstanding for CDS Contracts (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Ambac Rating
Notional outstanding	$ 1,313,797	$ 1,529,759
Other Derivatives [Member] | Successor [Member]
Ambac Rating
Notional outstanding	1,313,797	1,529,759
Other Derivatives [Member] | Successor [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding	0	0
Other Derivatives [Member] | Successor [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding	574,899	767,603
Other Derivatives [Member] | Successor [Member] | A Rating [Member]
Ambac Rating
Notional outstanding	9,322	43,160
Other Derivatives [Member] | Successor [Member] | BBB Rating [Member]
Ambac Rating
Notional outstanding	469,724	448,249
Other Derivatives [Member] | Successor [Member] | Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding	259,852	270,747
CLO [Member] | Successor [Member]
Ambac Rating
Notional outstanding	341,668	549,923
CLO [Member] | Other Derivatives [Member] | Successor [Member]
Ambac Rating
Notional outstanding	341,668	549,923
CLO [Member] | Other Derivatives [Member] | Successor [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding	0	0
CLO [Member] | Other Derivatives [Member] | Successor [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding	341,668	549,923
CLO [Member] | Other Derivatives [Member] | Successor [Member] | A Rating [Member] [Member]
Ambac Rating
Notional outstanding	0	0
Other [Member] | Successor [Member]
Ambac Rating
Notional outstanding	972,129	979,836
Other [Member] | Other Derivatives [Member] | Successor [Member]
Ambac Rating
Notional outstanding	972,129	979,836
Other [Member] | Other Derivatives [Member] | Successor [Member] | AAA Rating [Member]
Ambac Rating
Notional outstanding	0	0
Other [Member] | Other Derivatives [Member] | Successor [Member] | AA Rating [Member]
Ambac Rating
Notional outstanding	233,231	217,680
Other [Member] | Other Derivatives [Member] | Successor [Member] | A Rating [Member]
Ambac Rating
Notional outstanding	9,322	43,160
Other [Member] | Other Derivatives [Member] | Successor [Member] | BBB Rating [Member]
Ambac Rating
Notional outstanding	469,724	448,249
Other [Member] | Other Derivatives [Member] | Successor [Member] | Below Investment Grade Rating [Member]
Ambac Rating
Notional outstanding	$ 259,852	$ 270,747

Derivative Instruments - Summ76

Derivative Instruments - Summarize Information by Major Category of CDS Contracts (Detail) $ in Thousands	Sep. 30, 2015USD ($)Transactions	Dec. 31, 2014USD ($)Transactions
Summary of information by major category of CDS contracts
Gross principal notional outstanding	$ 1,313,797	$ 1,529,759
Successor [Member]
Summary of information by major category of CDS contracts
Number of CDS transactions | Transactions	14	16
CLO [Member] | Successor [Member]
Summary of information by major category of CDS contracts
Number of CDS transactions | Transactions	5	6
Gross principal notional outstanding	$ 341,668	$ 549,923
CLO [Member] | Successor [Member] | Credit Derivatives [Member]
Summary of information by major category of CDS contracts
Net derivative liabilities at fair value	$ 1,740	$ 2,027
Other [Member] | Successor [Member]
Summary of information by major category of CDS contracts
Number of CDS transactions | Transactions	9	10
Gross principal notional outstanding	$ 972,129	$ 979,836
Other [Member] | Successor [Member] | Credit Derivatives [Member]
Summary of information by major category of CDS contracts
Net derivative liabilities at fair value	$ 28,147	$ 71,432

Derivative Instruments - Summ77

Derivative Instruments - Summary of Notional Amounts of AFS's Trading Derivative Products (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	$ 1,313,797	$ 1,529,759
AFS [Member] | Successor [Member] | Interest Rate Swaps [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	757,135	782,904
AFS [Member] | Successor [Member] | Interest Rate Swaps-Pay-Fixed/Receive-Variable [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	1,446,248	1,479,650
AFS [Member] | Successor [Member] | Interest Rate Swaps-Basis Swaps [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	38,965	55,800
AFS [Member] | Successor [Member] | Futures Contracts [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	$ 75,000	$ 80,000

Derivative Instruments - Summ78

Derivative Instruments - Summary of Notional for VIE Derivatives Outstanding (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	$ 1,313,797	$ 1,529,759
Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member] | Interest Rate Swaps [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	1,659,640	1,710,344
Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member] | Interest Rate Swaps-Pay-Fixed/Receive-Variable [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	3,058,644	3,152,090
Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member] | Currency Swaps [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	378,050	724,656
Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member] | Credit Derivatives [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	$ 16,035	$ 18,278

Income Taxes - Major Jurisdicti

Income Taxes - Major Jurisdictions (Detail)	3 Months Ended
	Sep. 30, 2015
United States [Member]
Income Tax Contingency [Line Items]
Tax Year	2,010
New York State [Member]
Income Tax Contingency [Line Items]
Tax Year	2,011
New York City [Member]
Income Tax Contingency [Line Items]
Tax Year	2,011
United Kingdom [Member]
Income Tax Contingency [Line Items]
Tax Year	2,009
Italy [Member]
Income Tax Contingency [Line Items]
Tax Year	2,009

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2015USD ($)
Tax Credit Carryforward [Line Items]
NOL allocated amount	$ 4,831,481
Operating tax carryforward expiration year start	2,029
Operating tax carryforward expiration year end	2,034
U. S. Federal Net Operating Tax [Member]
Tax Credit Carryforward [Line Items]
NOL allocated amount	$ 4,596,127
United States [Member]
Tax Credit Carryforward [Line Items]
NOL allocated amount	143,491
United Kingdom [Member]
Tax Credit Carryforward [Line Items]
NOL allocated amount	$ 91,863

Income Taxes - Significant Port

Income Taxes - Significant Portions of Deferred Tax Liabilities and Deferred Tax Assets (Detail) - Successor [Member] - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Deferred tax liabilities:
Insurance intangible	$ 447,807	$ 493,822
Variable interest entities	15,615	14,149
Investments	147,881	138,072
Unearned premiums and credit fees	99,372	104,589
Other	33,768	33,835
Deferred Tax Liabilities, Gross	744,443	784,467
Deferred tax assets:
Net operating loss and capital carryforward	1,691,018	1,890,551
Loss reserves	119,427	185,881
Compensation	6,016	5,276
AMT Credits	18,439	10,359
Other	9,540	9,539
Sub total deferred tax assets	1,844,440	2,101,606
Valuation allowance	1,101,954	1,319,218
Total deferred tax assets	742,486	782,388
Deferred Tax Liabilities, Net	$ (1,957)	$ (2,079)

Income Taxes Income Taxes - Pro

Income Taxes Income Taxes - Provision for Income Taxes Charged To Income From Continuing Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Successor [Member]
Provision for Income Taxes [Line Items]
Income tax expense (benefit)	$ 2,838	$ 2,344	$ 8,464	$ 3,414

Income Taxes Income Taxes - Eff

Income Taxes Income Taxes - Effect of Income Taxes on Net Income and Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Successor [Member]
Income Tax Expense (Benefit) [Roll Forward]
Income tax expense (benefit)	$ 2,838	$ 2,344	$ 8,464	$ 3,414

Income Taxes Income Taxes - E84

Income Taxes Income Taxes - Effective Tax Rates Differing From Prevailing Federal Corporate Income Tax Rates (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Successor [Member]
Reconciliation of Effective Tax Rates [Line Items]
Provision for income taxes	$ 2,838	$ 2,344	$ 8,464	$ 3,414

Income Taxes Income Taxes - NOL

Income Taxes Income Taxes - NOL Usage Table (Details) $ in Thousands	Sep. 30, 2015USD ($)
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	$ 4,831,481

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2015USD ($)	Dec. 31, 2014USD ($)
Loss Contingencies [Line Items]
Number of RMBS Trustees Filing Suit		5
Litigation Settlement, Expense		$ 207
Successor [Member]
Loss Contingencies [Line Items]
Capital Leases, Future Minimum Payments, Remainder of Fiscal Year	$ 1,375,000
Operating Leases, Future Minimum Payments, Due in Two Years	6,168,000
Operating Leases, Future Minimum Payments, Due in Three Years	6,168,000
Operating Leases, Future Minimum Payments, Due Thereafter	14,947,000
Operating Leases, Future Minimum Payments Due	39,872,000
Capital Leases, Future Minimum Payments Due, Next Twelve Months	6,168,000
Capital Leases, Future Minimum Payments Due in Four Years	5,046,000
Settled Litigation [Member]
Loss Contingencies [Line Items]
Proceeds from Legal Settlements	$ 7,760,000

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2015Segment
Segment Reporting [Abstract]
Number of reportable segments	2

Segment Information - Summary o

Segment Information - Summary of Financial Information by Reportable Segment (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Revenues:
Total revenues before expenses and reorganization items	$ 87,690	$ 155,339	$ 473,933	$ 321,810
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	(388,193)	84,773	114,482	33,659
Total assets	24,266,919	26,590,785	24,266,919	26,590,785	$ 25,159,864
Net investment income	64,195	83,581	201,931	234,475
Amortization of insurance intangible assets	39,680	41,908	115,200	109,878
Interest expense	29,899	31,841	85,980	96,122
Goodwill, Impairment Loss	514,511	0	514,511	0	$ 0
Reorganization items	0	2	0	211
Unaffiliated Customers [Member]
Revenues:
Total revenues before expenses and reorganization items	86,565	154,968	470,725	321,439
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	(389,318)	84,402	111,274	33,288
Equity Method Investee [Member]
Revenues:
Total revenues before expenses and reorganization items	1,125	371	3,208	371
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	1,125	371	3,208	371
Financial Guarantee [Member]
Revenues:
Total revenues before expenses and reorganization items	152,048		521,626	438,528
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	(321,177)	95,534	170,184	132,556
Financial Services [Member]
Revenues:
Total revenues before expenses and reorganization items	(67,201)		(54,131)	(117,195)
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	(67,230)	(16,585)	(56,000)	(120,437)
Corporate, Non-Segment [Member]
Revenues:
Total revenues before expenses and reorganization items	2,915	6,287	6,547	23,822
Inter-segment Eliminations [Member]
Revenues:
Total revenues before expenses and reorganization items	(72)	(5,856)	(109)	(23,345)
Operating Segments [Member] | Financial Guarantee [Member]
Revenues:
Total revenues before expenses and reorganization items	24	170,572
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations		(6,441)
Total assets	23,610,582	25,926,306	23,610,582	25,926,306
Net investment income	61,292	82,978	195,270	232,995
Amortization of insurance intangible assets	39,680	41,908	115,200	109,878
Interest expense	29,738	31,491	85,165	94,886
Goodwill, Impairment Loss	514,511		514,511
Operating Segments [Member] | Financial Guarantee [Member] | Unaffiliated Customers [Member]
Revenues:
Total revenues before expenses and reorganization items	152,024	170,335	521,340	437,591
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	(320,414)	101,975	172,271	157,551
Operating Segments [Member] | Financial Guarantee [Member] | Equity Method Investee [Member]
Revenues:
Total revenues before expenses and reorganization items	0	0	0	0
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	0	0	0	0
Operating Segments [Member] | Financial Guarantee [Member] | Inter-segment Eliminations [Member]
Revenues:
Total revenues before expenses and reorganization items		237
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	(763)
Operating Segments [Member] | Financial Services [Member]
Revenues:
Total revenues before expenses and reorganization items	(204)	(15,664)
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations		(281)
Total assets	363,118	349,411	363,118	349,411
Net investment income	139	154	401	967
Amortization of insurance intangible assets	0	0	0	0
Interest expense	161	350	815	1,236
Goodwill, Impairment Loss	0		0
Operating Segments [Member] | Financial Services [Member] | Unaffiliated Customers [Member]
Revenues:
Total revenues before expenses and reorganization items	(66,997)	(15,445)	(53,566)	(116,294)
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	(67,655)	(16,304)	(55,861)	(119,287)
Operating Segments [Member] | Financial Services [Member] | Equity Method Investee [Member]
Revenues:
Total revenues before expenses and reorganization items	0	0	0	0
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	0	0	0	0
Operating Segments [Member] | Financial Services [Member] | Inter-segment Eliminations [Member]
Revenues:
Total revenues before expenses and reorganization items		(219)
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	425
Inter-segment Eliminations [Member]
Revenues:
Total revenues before expenses and reorganization items	(72)	(5,856)	(109)	(23,345)
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	(964)	0	(801)	0
Total assets	3,981	16,195	3,981	16,195
Net investment income	0	0	0	0
Amortization of insurance intangible assets	0	0	0	0
Interest expense	0	0	0	0
Goodwill, Impairment Loss	0		0
Inter-segment Eliminations [Member] | Unaffiliated Customers [Member]
Revenues:
Total revenues before expenses and reorganization items	0	0	0	0
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	0	0	0	0
Inter-segment Eliminations [Member] | Equity Method Investee [Member]
Revenues:
Total revenues before expenses and reorganization items	0	0	0	0
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	0	0	0	0
Inter-segment Eliminations [Member] | Financial Guarantee [Member]
Revenues:
Total revenues before expenses and reorganization items			286	937
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations			(2,087)	(24,995)
Inter-segment Eliminations [Member] | Financial Services [Member]
Revenues:
Total revenues before expenses and reorganization items			(565)	(901)
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations			(139)	(1,150)
Inter-segment Eliminations [Member] | Corporate, Non-Segment [Member]
Revenues:
Total revenues before expenses and reorganization items	252	5,838	388	23,309
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	1,302	6,722	3,027	26,145
Corporate, Non-Segment [Member]
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	1,178	5,824	1,099	21,540
Total assets	289,238	298,873	289,238	298,873
Net investment income	2,764	449	6,260	513
Amortization of insurance intangible assets	0	0	0	0
Corporate, Non-Segment [Member] | Unaffiliated Customers [Member]
Revenues:
Total revenues before expenses and reorganization items	1,538	78	2,951	142
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	(1,249)	(1,269)	(5,136)	(4,976)
Corporate, Non-Segment [Member] | Equity Method Investee [Member]
Revenues:
Total revenues before expenses and reorganization items	1,125		3,208	371
Pre-tax income (loss) from continuing operations:
Pre-tax (loss) income from continuing operations	1,125		3,208	371
Corporate, Non-Segment [Member] | Corporate, Non-Segment [Member]
Pre-tax income (loss) from continuing operations:
Interest expense	0	$ 0	0	$ 0
Goodwill, Impairment Loss	$ 0		$ 0

Segment Information - Schedule

Segment Information - Schedule of Gross Premiums Written, Net Premiums Earned and Net Change in Fair Value of Credit Derivatives (Detail) - Successor [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Gross Premiums Written	$ (8,710)	$ (13,700)	$ (18,840)	$ (64,952)
Net premiums earned	71,535	64,831	198,132	212,391
Net Change In Fair Value Of Credit Derivatives	36,952	7,416	44,746	13,579
Reportable Geographical Components [Member] | United States [Member]
Segment Reporting Information [Line Items]
Gross Premiums Written	(2,386)	(15,355)	(5,172)	(44,266)
Net premiums earned	60,402	44,882	163,094	141,472
Net Change In Fair Value Of Credit Derivatives	30,604	262	39,286	6,283
Reportable Geographical Components [Member] | United Kingdom [Member]
Segment Reporting Information [Line Items]
Gross Premiums Written	260	1,482	7,295	(1,681)
Net premiums earned	8,081	14,309	23,659	55,752
Net Change In Fair Value Of Credit Derivatives	0	0	0	0
Reportable Geographical Components [Member] | Other International [Member]
Segment Reporting Information [Line Items]
Gross Premiums Written	(6,584)	173	(20,963)	(19,005)
Net premiums earned	3,052	5,640	11,379	15,167
Net Change In Fair Value Of Credit Derivatives	$ 6,348	$ 7,154	$ 5,460	$ 7,296