Ambac Financial (AMBC) 10-Q 5 Aug 24 2024 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - $ / shares	6 Months Ended
	Jun. 30, 2024	Aug. 02, 2024	Apr. 30, 2013
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2024
Entity Ex Transition Period	false
Entity File Number	1-10777
Entity Registrant Name	AMBAC FINANCIAL GROUP, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	13-3621676
Entity Address, Address Line One	One World Trade Center
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10007
City Area Code	(212)
Local Phone Number	658-7470
Title of 12(b) Security	Common stock par value $0.01 per share
Trading Symbol	AMBC
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Bankruptcy Proceedings, Reporting Current	true
Entity Common Stock, Shares Outstanding		47,440,995
Common Stock, Par or Stated Value Per Share	$ 0.01		$ 0.01
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Entity Central Index Key	0000874501
Current Fiscal Year End Date	--12-31

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Assets:
Fixed maturity securities, at fair value	$ 2,043,000	$ 2,043,000
Total investments (net of allowance for credit losses of $3 and $3)	2,632,000	2,632,000	$ 2,664,000
Restricted Cash	11,000	11,000	12,000
Premiums Receivable, Net	317,000	317,000	290,000
Premium Receivable, Allowance for Credit Loss	3,000	3,000	4,000
Reinsurance Recoverables on Unpaid Losses, Allowance	0	0	0
Reinsurance Recoverables, Including Reinsurance Premium Paid	277,000	277,000	195,000
Deferred ceded premium	232,000	232,000	204,000
Subrogation recoverable	128,000	128,000	137,000
Derivative assets	18,000	18,000	26,000
Intangible assets, less accumulated amortization	285,000	285,000	307,000
Goodwill	70,000	70,000	70,000	$ 61,000
Other assets	163,000	163,000	129,000
Total assets	8,184,000	8,184,000	8,428,000
Liabilities:
Unearned premiums	445,000	445,000	422,000
Liability for Claims and Claims Adjustment Expense	890,000	890,000	893,000
Ceded premiums payable	140,000	140,000	90,000
Long-term debt	515,000	515,000	508,000
Accrued interest payable	500,000	500,000	475,000
Derivative Liability	26,000	26,000	35,000
Other liabilities	203,000	203,000	199,000
Total liabilities	6,748,000	6,748,000	6,997,000
Redeemable Noncontrolling Interest, Equity, Redemption Value	17,000	17,000
Redeemable Noncontrolling Interest, Equity, Carrying Amount	17,000	17,000	17,000	20,000
Liabilities	6,748,000	6,748,000	6,997,000
Stockholders’ equity:
Preferred stock, par value $0.01 per share; 20,000,000 shares authorized; issued and outstanding shares—none	0	0	0
Common Stock, Value, Issued	0	0	0
Additional paid-in capital	295,000	295,000	292,000
Accumulated other comprehensive income	(175,000)	(175,000)	(160,000)	(253,000)
Retained earnings	1,265,000	1,265,000	1,246,000
Treasury stock, shares at cost: 0 and 8,202	(17,000)	(17,000)	(17,000)
Total Ambac Financial Group, Inc. stockholders’ equity	1,368,000	1,368,000	1,362,000
Noncontrolling interest	51,000	51,000	53,000
Total stockholders’ equity	1,419,000	1,419,000	1,415,000	1,305,000
Total liabilities and stockholders’ equity	8,184,000	8,184,000	8,428,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	3,000	3,000	3,000
Debt Securities, Available-for-sale, Amortized Cost	2,078,000	2,078,000	2,197,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	97,000	97,000	274,000	$ 61,000
Deferred Policy Acquisition Cost	12,000	12,000	11,000
Capitalized Contract Cost, Net	$ 7,000	$ 7,000	$ 6,000
Treasury Stock, Common, Shares	1,434,172	1,434,172	1,463,774
Preferred Stock, Shares Issued	0	0	0
Afg [Member]
Stockholders’ equity:
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 35,000	$ 35,000	$ 28,000
Short-term Investments [Member]
Assets:
Fixed maturity securities, at fair value	314,000	314,000	426,000
Stockholders’ equity:
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Amortized Cost	314,000	314,000	426,000
Variable Interest Entity, Primary Beneficiary [Member]
Assets:
Fixed maturity securities, at fair value	2,101,000	2,101,000	2,167,000
Restricted Cash	62,000	62,000	246,000
Derivative assets	208,000	208,000	226,000
Other assets	95,000	95,000	92,000
Total assets	4,033,000	4,033,000	4,394,000
Liabilities:
Long-term debt	2,853,000	2,853,000	2,967,000
Derivative Liability	1,136,000	1,136,000	1,197,000
Other Sundry Liabilities, Current	59,000	59,000	240,000
Other liabilities	7,000	7,000	5,000
Total liabilities	4,048,000	4,048,000	4,404,000
Liabilities	4,048,000	4,048,000	4,404,000
Stockholders’ equity:
Financing Receivable, after Allowance for Credit Loss	1,567,000	1,567,000	1,663,000
Gross Investment Income, Operating	2,000
Derivative and other assets	303,000	303,000	318,000
Fixed Income Securities [Member]
Assets:
Fixed maturity securities, at fair value	1,703,000	1,703,000	1,710,000
Stockholders’ equity:
Debt Securities, Available-for-sale, Allowance for Credit Loss	3,000	3,000	3,000
Debt Securities, Available-for-sale, Amortized Cost	1,737,000	1,737,000	1,744,000
Debt Securities, Available-for-Sale, Excluding Accrued Interest	1,703,000	1,703,000	1,710,000
Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, before Allowance for Credit Loss	1,737,000	1,737,000	1,744,000
Short-term Investments [Member]
Assets:
Fixed maturity securities, at fair value	314,000	314,000	426,000
Stockholders’ equity:
Gross Investment Income, Operating	5,000	10,000
Other Investments [Member]
Stockholders’ equity:
Other Investment Not Readily Marketable, Fair Value	558,000	558,000	475,000
Gross Investment Income, Operating	8,000	21,000
Fixed Income Securities, Trading
Stockholders’ equity:
Gross Investment Income, Operating	2,000	4,000
Debt Securities, Available-for-Sale, Excluding Accrued Interest	31,000	31,000	27,000
Collateral Pledged [Member] | Fixed Income Securities [Member]
Assets:
Fixed maturity securities, at fair value	25,000	25,000	27,000
Stockholders’ equity:
Debt Securities, Available-for-sale, Amortized Cost	27,000	27,000	0
Collateral Pledged [Member] | Fixed Income Securities [Member] | Short-term Investments [Member]
Assets:
Fixed maturity securities, at fair value	0	0	27,000
Stockholders’ equity:
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0	0
Debt Securities, Available-for-sale, Amortized Cost	0	0	27,000
Collateral Pledged [Member] | Short-term Investments
Stockholders’ equity:
Debt Securities, Available-for-sale, Amortized Cost	0	0	27,000
Collateralized Securities | Fixed Income Securities [Member]
Stockholders’ equity:
Debt Securities, Available-for-Sale, Excluding Accrued Interest	25,000	25,000	0
Collateralized Securities | Short-term Investments [Member]
Assets:
Fixed maturity securities, at fair value	$ 0	$ 0	$ 27,000

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale, Amortized Cost	$ 2,078	$ 2,197
Debt Securities, Available-for-sale, Allowance for Credit Loss	3	3
Premium Receivable, Allowance for Credit Loss	$ 3	$ 4
Preferred stock, par value	$ 0.01
Preferred stock, shares authorized	20,000,000
Preferred Stock, Shares Issued	0	0
Common stock, par value	$ 0.01
Common stock, shares authorized	130,000,000
Common stock, shares issued	46,659,144	46,659,144
Common stock, shares outstanding	45,224,972
Equity investments in pooled funds [Member]
Other Investment Not Readily Marketable, Fair Value	$ 533	$ 463
Variable Interest Entity, Primary Beneficiary [Member]
Long-term debt	$ 2,599	$ 2,710

Consolidated Statements of Tota

Consolidated Statements of Total Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Net investment income:
Interest Income, Debt Securities, Available-for-Sale, Operating	$ 26,000	$ 22,000	$ 52,000	$ 43,000
Net investment income	36,000	35,000	78,000	69,000
Realized Investment Gains (Losses)	4,000	(3,000)	4,000	(8,000)
Change in fair value of credit derivatives:
Derivative, Gain (Loss) on Derivative, Net	0	0	2,000	(3,000)
Insurance Commissions and Fees	13,000	10,000	31,000	25,000
Other Operating Income (Expense), Net	16,000	2,000	18,000	5,000
Income (loss) on variable interest entities	0	0	2,000	(1,000)
Total revenues and other income	105,000	62,000	207,000	120,000
Policyholder Benefits and Claims Incurred, Net	18,000	7,000	16,000	25,000
Expenses:
Intangible amortization	8,000	7,000	21,000	13,000
General and Administrative Expense	47,000	36,000	83,000	72,000
Interest expense	16,000	16,000	32,000	32,000
Total expenses	103,000	73,000	180,000	160,000
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	2,000	(11,000)	27,000	(40,000)
Provision for income taxes	2,000	2,000	7,000	6,000
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	0	0	(1,000)	(1,000)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(1,000)	(13,000)	20,000	(46,000)
Net income (loss) attributable to common stockholders	(1,000)	(13,000)	19,000	(47,000)
Other comprehensive income (loss), after tax
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(1,000)	(13,000)	20,000	(46,000)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	4,000	(13,000)	(3,000)	5,000
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	1,000	21,000	(7,000)	37,000
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, after Tax	0	0	0	0
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	(5,000)	0	(5,000)	2,000
Total other comprehensive income (loss), net of income tax	0	8,000	(15,000)	44,000
Total comprehensive income (loss), net of income tax	0	(5,000)	5,000	(2,000)
Less: comprehensive (gain) loss attributable to the noncontrolling interest
Total comprehensive income (loss) attributable to common stockholders	0	(6,000)	4,000	(3,000)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest	$ 0	$ 0	$ (1,000)	$ (1,000)
Earnings Per Share, Basic	$ (0.02)	$ (0.29)	$ 0.42	$ (1.02)
Earnings Per Share, Diluted	$ (0.02)	$ (0.29)	$ 0.41	$ (1.02)
Weighted Average Number of Shares Outstanding, Basic	46,209,250	45,757,234	46,019,145	45,661,288
Weighted Average Number of Shares Outstanding, Diluted	46,209,250	45,757,234	46,568,862	45,661,288
Gain (loss) on foreign currency translation, taxes	$ 0	$ 0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Plan Amendments, Tax Effect	0	0
Premiums Earned, Net	33,000	15,000	$ 66,000	$ 29,000
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	3,000	2,000	6,000	4,000
Deferred Policy Acquisition Costs, Amortization Expense	5,000	1,000	10,000	3,000
General and Administrative Expense	47,000	36,000	83,000	72,000
Insurance Commissions	8,000	6,000	18,000	14,000
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Plan Amendments, Tax Effect	0	0
Gain (loss) on foreign currency translation, taxes	0	0
Unrealized (loss) gain on securities, taxes	0	$ (3,000)	$ 0	$ (1,000)
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, Tax	$ 0

Consolidated Statements of To_2

Consolidated Statements of Total Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Statement [Abstract]
Unrealized (loss) gain on securities, taxes	$ 0	$ (3)	$ 0	$ (1)
Gain (loss) on foreign currency translation, taxes	0	0
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, Tax	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Plan Amendments, Tax Effect	$ 0	$ 0

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Treasury Stock, Common	Noncontrolling Interest [Member]
Beginning balance at Dec. 31, 2022	$ 1,305	$ 0	$ 0	$ 274	$ (253)	$ 1,245	$ (15)	$ 53
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	(3)
Stock-based compensation	8			8
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	(5)					(8)	3	0
Ending balance at Jun. 30, 2023	1,303	0	0	283	(209)	1,191	(15)	53
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury Stock, Value, Acquired, Cost Method	(3)						(3)
Total comprehensive income (loss)	(2)				44	(47)		0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	44
Noncontrolling Interest, Change in Redemption Value	0
Beginning balance at Mar. 31, 2023	1,307	0	0	278	(217)	1,206	(14)	53
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	(6)				8	(13)		0
Stock-based compensation	5			5
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	0	0	0		0	(2)	2
Ending balance at Jun. 30, 2023	1,303	0	0	283	(209)	1,191	(15)	53
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	(5)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	8
Noncontrolling Interest, Change in Redemption Value	0					0
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable								0
Beginning balance at Dec. 31, 2023	1,415	0	0	292	(160)	1,246	(17)	53
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	4
Stock-based compensation	2			2
Shares Issued, Value, Share-based Payment Arrangement, after Forfeiture	(1)					(1)	0	0
Ending balance at Jun. 30, 2024	1,419	0	0	295	(175)	1,265	(17)	51
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	5				(15)	19		0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(15)
Noncontrolling Interest, Change in Redemption Value	0					0
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable								0
Payments to Acquire Interest in Subsidiaries and Affiliates	(1)			1				(2)
Beginning balance at Mar. 31, 2024	1,418	0	0	291	(175)	1,266	(17)	53
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	0
Stock-based compensation	2			2
Ending balance at Jun. 30, 2024	1,419	$ 0	$ 0	295	(175)	1,265	$ (17)	51
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Total comprehensive income (loss)	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	0				$ 0	(1)		0
Noncontrolling Interest, Change in Redemption Value	0					$ 0
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Nonredeemable								0
Payments to Acquire Interest in Subsidiaries and Affiliates	$ (1)			$ 1				$ (2)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Cash flows from operating activities:
Net income attributable to common shareholders	$ 19,000	$ (47,000)
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	(1,000)	(1,000)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total	20,000	(46,000)
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	1,000	1,000
Amortization of bond premium and discount	(8,000)	(6,000)
Share-based compensation	2,000	8,000
Unearned premiums, net	(5,000)	(51,000)
Losses and loss expenses, net	(15,000)	144,000
Ceded premiums payable	50,000	57,000
Premium receivables	(27,000)	(7,000)
Accrued interest payable	25,000	(26,000)
Amortization of Intangible Assets	21,000	13,000
Net investment gains (losses), including impairments	(4,000)	8,000
Variable interest entity activities	(2,000)	1,000
Other, net	(24,000)	4,000
Net Cash Provided by (Used in) Operating Activities, Total	32,000	101,000
Proceeds from Sale of Debt Securities, Available-for-Sale	26,000	107,000
Net Cash Provided by (Used in) Investing Activities [Abstract]
Proceeds from matured bonds	76,000	31,000
Purchases of bonds	(215,000)	(226,000)
Proceeds from sales of other invested assets	41,000	108,000
Purchases of other invested assets	(94,000)	(42,000)
Change in short-term investments	139,000	170,000
Change in cash collateral	5,000	(37,000)
Proceeds from paydowns of consolidated VIE assets	84,000	113,000
Other, net	(1,000)	10,000
Net cash provided by (used in) investing activities	(120,000)	489,000
Net Cash Provided by (Used in) Financing Activities [Abstract]
Tax payments related to shares withheld for share-based compensation plans	(1,000)	(8,000)
Proceeds from (Payments to) Noncontrolling Interests	(1,000)	(1,000)
Payments of consolidated VIE liabilities, net	(87,000)	(235,000)
Net cash used in financing activities	(89,000)	(343,000)
Effect of foreign exchange on cash, cash equivalents and restricted cash	0	1,000
Net cash flow	(178,000)	248,000
Cash, cash equivalents, and restricted cash at beginning of period	274,000	61,000
Cash, cash equivalents, and restricted cash at end of period	97,000	309,000
Change in cash collateral	5,000	(37,000)
Treasury Stock, Value, Acquired, Cost Method		(3,000)
Tier 2 Notes
Net Cash Provided by (Used in) Financing Activities [Abstract]
Repayments of Secured Debt	0	(97,000)
Repayments of Secured Debt	0	97,000
Variable Interest Entity, Primary Beneficiary [Member]
Net Cash Provided by (Used in) Investing Activities [Abstract]
Change in cash collateral	(180,000)	256,000
Change in cash collateral	$ (180,000)	$ 256,000

Business and Basis of Presentat

Business and Basis of Presentation Background and Business Description (Notes)	6 Months Ended
	Mar. 31, 2025	Jun. 30, 2024
Accounting Policies [Abstract]
Background and Business Description		1. BUSINESS AND BASIS OF PRESENTATION Business The following description provides an update of Note 1. Background and Business Description and Note 2. Basis of Presentation and Significant Accounting Policies in the Notes to the Consolidated Financial Statements included in Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023, and should be read in conjunction with the complete descriptions provided in the Form 10-K. Capitalized terms used, but not defined herein, and in the other footnotes to the Consolidated Financial Statements included in this Quarterly Report on Form 10-Q shall have the meanings ascribed thereto in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. Ambac Financial Group, Inc. (“AFG”), headquartered in New York City, is a specialty insurance holding company incorporated in the state of Delaware on April 29, 1991. References to “Ambac,” the “Company,” “we,” “our,” and “us” are to AFG and its subsidiaries, as the context requires. Ambac's principal businesses include: • Specialty Property & Casualty Insurance — Ambac's Specialty Property & Casualty Insurance program business. Currently includes six carriers (collectively, “Everspan”). Everspan carriers have an A.M. Best rating of 'A-' (Excellent) that was affirmed on June 13, 2024. • Insurance Distribution — Ambac's specialty property and casualty ("P&C") insurance distribution business, which could include Managing General Agents and Underwriters (collectively "MGAs"), insurance brokers, and other distribution businesses. At June 30, 2024 Ambac's insurance distribution platform includes five businesses that operate in the following lines of business: accident and health, specialty commercial automobile insurance for specific "for-hire" auto clauses, marine and international risk and professional liability. • Legacy Financial Guarantee Insurance — Ambac's legacy financial guarantee business includes the activities of Ambac Assurance Corporation ("AAC") and its wholly owned subsidiaries, including Ambac Assurance UK Limited (“Ambac UK”) and Ambac Financial Services LLC ("AFS"). Both AAC and Ambac UK (the "Legacy Financial Guarantee Companies") have financial guarantee insurance portfolios that have been in runoff since 2008. AFS provided interest rate derivatives to financial guarantee customers and used derivatives to hedge interest rate risk in AAC's insurance and investment portfolios. AFS' remaining derivative positions include a limited number of legacy customer swaps and their associated hedges. The Company reports these three business operations as segments; see Note 2. Segment Information for further information.
Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block]	1. BUSINESS AND BASIS OF PRESENTATION Business The following description provides an update of Note 1. Background and Business Description and Note 2. Basis of Presentation and Significant Accounting Policies in the Notes to the Consolidated Financial Statements included in Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023, and should be read in conjunction with the complete descriptions provided in the Form 10-K. Capitalized terms used, but not defined herein, and in the other footnotes to the Consolidated Financial Statements included in this Quarterly Report on Form 10-Q shall have the meanings ascribed thereto in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. Ambac Financial Group, Inc. (“AFG”), headquartered in New York City, is a specialty insurance holding company incorporated in the state of Delaware on April 29, 1991. References to “Ambac,” the “Company,” “we,” “our,” and “us” are to AFG and its subsidiaries, as the context requires. Ambac's principal businesses include: • Specialty Property & Casualty Insurance — Ambac's Specialty Property & Casualty Insurance program business. Currently includes six carriers (collectively, “Everspan”). Everspan carriers have an A.M. Best rating of 'A-' (Excellent) that was affirmed on June 13, 2024. • Insurance Distribution — Ambac's specialty property and casualty ("P&C") insurance distribution business, which could include Managing General Agents and Underwriters (collectively "MGAs"), insurance brokers, and other distribution businesses. At June 30, 2024 Ambac's insurance distribution platform includes five businesses that operate in the following lines of business: accident and health, specialty commercial automobile insurance for specific "for-hire" auto clauses, marine and international risk and professional liability. • Legacy Financial Guarantee Insurance — Ambac's legacy financial guarantee business includes the activities of Ambac Assurance Corporation ("AAC") and its wholly owned subsidiaries, including Ambac Assurance UK Limited (“Ambac UK”) and Ambac Financial Services LLC ("AFS"). Both AAC and Ambac UK (the "Legacy Financial Guarantee Companies") have financial guarantee insurance portfolios that have been in runoff since 2008. AFS provided interest rate derivatives to financial guarantee customers and used derivatives to hedge interest rate risk in AAC's insurance and investment portfolios. AFS' remaining derivative positions include a limited number of legacy customer swaps and their associated hedges. The Company reports these three business operations as segments; see Note 2. Segment Information for further information. Sale of Ambac Assurance Corporation ("AAC") On June 4, 2024, AFG entered into a stock purchase agreement (the "Purchase Agreement") with American Acorn Corporation (the “Buyer”), a Delaware corporation owned by funds managed by Oaktree Capital Management, L.P., pursuant to which and subject to the conditions set forth therein, AFG will sell all of the issued and outstanding shares of common stock of AAC, a wholly-owned subsidiary of AFG, to Buyer for aggregate consideration of $420 in cash (the "Sale"). The terms of the Sale as contemplated by the Purchase Agreement provide that, at the closing of the Sale (the “Closing”), Buyer will acquire complete ownership of the common stock of AAC and all of its wholly owned subsidiaries, including Ambac UK. The Purchase Agreement provides that AFG will seek the affirmative vote in favor of the Sale by the holders of a majority of the issued and outstanding shares of AFG common stock entitled to vote thereon (the “Stockholder Approval”). On August 2, 2024, AFG filed a preliminary proxy statement with the SEC, which proxy statement includes the recommendation of the board of directors of AFG that the Sale be approved by shareholders of AFG. The Purchase Agreement contains certain customary termination rights for each of AFG and Buyer, including (i) by mutual written agreement, (ii) if the Sale has not been consummated on or before April 4, 2025 (the “End Date”), subject to certain extensions for 90 days, (iii) the other party is in breach of the Purchase Agreement in a manner that would result in a failure of an applicable closing condition and such breach cannot be cured or, if curable, has not been cured within 60 days after written notice to the other party of such breach, (iv) the Stockholder Approval is not received, or (v) if any applicable law makes the consummation of the Closing illegal or otherwise prohibited or any judgment, order or decree of any governmental authority enjoins Buyer and AFG from consummating the Closing. In addition, Buyer may terminate the Purchase Agreement if AFG changes its recommendation to AFG's stockholders regarding the Sale. AFG would pay Buyer an amount equal to $22 (the “Termination Fee”) if all of the following occur: (i) the Purchase Agreement is terminated as a result of (a) not closing the Sale and other transactions contemplated by the Purchase Agreement by the End Date, subject to certain conditional extension for 90 days, (b) failure to obtain the Stockholder Approval or (c) an AFG breach of representations or covenants that would cause certain closing conditions not to be satisfied, (ii) AFG has received an alternative acquisition proposal prior to a valid termination of the Purchase Agreement, and (iii) within 12 months after termination of the Purchase Agreement, AFG enters into a definitive agreement for an alternative acquisition. AFG would also pay Buyer the Termination Fee if the Purchase Agreement is terminated for (x) AFG breach of certain covenants that would cause closing conditions not to be satisfied, (y) failure to obtain the Stockholder Approval at a time when Buyer could have terminated the Purchase Agreement for an AFG breach of certain covenants that would cause closing conditions not to be satisfied, or (z) AFG changing its recommendation to the Company’s stockholders regarding the sale. In addition to the Termination Fee, AFG would pay Buyer up to $6 as a reimbursement of Buyer’s reasonably documented out-of-pocket fees and expenses incurred in connection with the Sale and other transactions contemplated by the Purchase Agreement if (i) the Purchase Agreement is terminated as a result of not closing the Sale and other transactions by the End Date and the Termination Fee is also payable, (ii) there is a failure to obtain the Stockholder Approval when the Buyer could have terminated the Purchase Agreement because there is an AFG breach of representations or covenants related to regulatory efforts, non-solicitation or the AFG stockholders meeting that would cause certain closing conditions not to be satisfied, (iii) the Purchase Agreement is terminated as a result of AFG changing its recommendation to the AFG stockholders regarding the Sale, or (iv) there is an AFG breach of representations or covenants that would cause certain closing conditions not to be satisfied. The Closing is subject to customary closing conditions, including the receipt of specified regulatory approvals and the Stockholder Approval. In connection with and pursuant to the Purchase Agreement, AFG has agreed to issue to Buyer a warrant exercisable for a number of shares of common stock, par value $0.01, of AFG representing 9.9% of the fully diluted shares of AFG’s common stock as of March 31, 2024, pro forma for the issuance of the Warrant. The Warrant will have an exercise price per share of $18.50 with a 6.5 year term from the date of issuance and will be immediately exercisable. Payment of the exercise price may be settled, at AFG’s option, by way of a cash exercise or by net share settlement. While management and the Board have approved the Sale, the final commitment to sell AAC is subject to approval by our shareholders and regulators in both the US and UK. The Sale will have a major effect on AFG's operations and financial results and therefore at the date we meet the held-for-sale reporting requirements, we will report the pending sale as a discontinued operation. At June 30, 2024, the carrying value of AFG's investment in AAC is approximately $939. Once the shareholders vote is obtained and regulatory approval is probable, a loss on the transaction will be reflected in the Statement of Comprehensive Income equal to the difference between the sales proceeds (net of the value of the Warrants to be issued) and AAC's carrying value. Additionally, net income will be adversely impacted by a reclassification from Accumulated Other Comprehensive Income relating to unrealized losses on available-for-sale investment securities, foreign currency translation losses and credit risk changes of fair value option liabilities, which at June 30, 2024 amounted to $168. The Sale is expected to close in the fourth quarter of 2024 or the first quarter of 2025. Acquisition of Beat Capital Partners Limited ("Beat") On June 4, 2024, the Company, entered into a share purchase agreement (the “Beat Purchase Agreement”), by and among the Company, Cirrata V LLC, a Delaware limited liability company and an indirect wholly owned subsidiary of AFG (the “Purchaser”), certain sellers set forth therein (the “Sellers”) and Beat, pursuant to which, effective July 31, 2024, the Purchaser purchased from the Sellers approximately 60% of the entire issued share capital of Beat for total consideration, as of the closing date, of approximately $278, of which approximately $249 was paid in cash and the remainder of which was satisfied through the issuance of 2,216,023 shares of AFG common stock to certain Sellers (the "Beat Transaction"). Beat’s management team and Bain Capital Credit LP (“Bain” and, together with certain members of Beat’s management team, the “Rollover Shareholders”) each retained approximately 20% of Beat’s issued share capital immediately after closing. AFG guaranteed the Purchaser’s performance under the Beat Purchase Agreement and the Shareholders’ Agreement (as defined below). AFG issued the common stock free and clear of any liens or restrictions (other than those arising under state and federal securities laws of the United States) and bearing a restrictive legend. The common stock has not been registered under the Securities Act in reliance upon an exemption from registration pursuant to Section 4(a)(2) of the Securities Act. AFG funded the cash portion of the consideration with a combination of available cash, approximately $65 of funding from AAC, and $150 of new indebtedness (the "Credit Facility") that was issued in the third quarter of 2024. Funding received from AAC and the Credit Facility are required to be repaid upon closing of the sale of AAC. To reduce its exposure to appreciation of the British Pound Sterling ("GBP") relative to the U.S. Dollar ("USD"), AFG entered into a foreign exchange futures contract under which it agreed to purchase an amount of GBP sufficient to cover the cash portion of the purchase price of Beat along with estimated GBP denominated expenses at an exchange rate of 1.2662 per USD. At the closing of the Beat Transaction, AFG entered into a Shareholders’ Agreement by and among AFG, the Purchaser, the Rollover Shareholders and Beat (the “Shareholders’ Agreement”). The Shareholders’ Agreement provides for, among other things, the granting of (i) put options to each Rollover Shareholder to require the Purchaser to purchase from such Rollover Shareholder, the Relevant Shares (as defined in the Shareholders’ Agreement), and (ii) call options to the Purchaser to purchase from each Rollover Shareholder, the Relevant Shares. Basis of Presentation The Company has disclosed its 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, 2023. The following significant accounting policies provide an update to those included in the Company’s Annual Report on Form 10-K. 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 consolidated 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, 2023. 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 necessary for the fair presentation of the Company’s consolidated financial position and results of operations. The results of operations for the three and six months ended June 30, 2024, may not be indicative of the results that may be expected for the year ending December 31, 2024. The December 31, 2023, 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. Consolidation The consolidated financial statements include the accounts of AFG and all other entities in which AFG (directly or through its subsidiaries) has a controlling financial interest, including variable interest entities (“VIEs”) for which AFG or an AFG subsidiary is deemed the primary beneficiary in accordance with the Consolidation Topic of the Accounting Standards Codification ("ASC"). All significant intercompany balances have been eliminated. See Note 8. Variable Interest Entities , for a detailed discussion of Ambac’s involvement in VIEs, Ambac’s methodology for determining whether Ambac is required to consolidate a VIE and the effects of VIEs being consolidated and deconsolidated. Foreign Currency The impact of non-functional currency transactions and the remeasurement of non-functional currency assets and liabilities into the respective subsidiaries' functional currency (collectively "foreign currency transactions gains/(losses)") are $(1) and $(3) for the six months ended June 30, 2024 and 2023, respectively. Foreign currency transactions gains/(losses) are primarily the result of remeasuring Ambac UK's assets and liabilities denominated in currencies (primarily the U.S. dollar and the Euro) other than its functional currency (the British Pound Sterling). Redeemable Noncontrolling Interest The Riverton, All Trans, Capacity Marine and Xchange acquisitions resulted in a majority ownership of the acquired entities by Ambac. Under the terms of all the acquisition agreements, Ambac has call options to purchase the remaining interests from the minority owners (i.e., noncontrolling interests) and the minority owners have put options to sell their interests to Ambac. Because the exercise of the put options are outside the control of Ambac, in accordance with the Distinguishing Liabilities from Equity Topic of the ASC, Ambac reports redeemable noncontrolling interests in the mezzanine section of its consolidated balance sheet. The redeemable noncontrolling interest is remeasured each period as the greater of: i. the carrying value under ASC 810, which attributes a portion of consolidated net income (loss) to the redeemable noncontrolling interest, and ii. the redemption value of the put option under ASC 480 as if it were exercisable at the end of the reporting period. Any increase (decrease) in the carrying amount of the redeemable noncontrolling interest as a result of adjusting to the redemption value of the put option is recorded as an offset to retained earnings. The impact of such differences on earnings per share are presented in Note 11. Net Income Per Share . Following is a rollforward of redeemable noncontrolling interest. Six Months Ended June 30, 2024 2023 Beginning balance $ 17 $ 20 Fair value of redeemable noncontrolling interest at acquisition date — — Net income attributable to redeemable noncontrolling interest (ASC 810) 1 1 Distributions (1) (1) Adjustment to redemption value (ASC 480) — — Ending balance $ 17 $ 20 Supplemental Disclosure of Cash Flow Information Six Months Ended June 30, 2024 2023 Cash paid during the period for: Income taxes $ 7 $ 6 Interest on long-term debt — 50 Non-cash investing and financing activities: Securities acquired (transferred) in transactions related to Puerto Rico restructurings — (1) Securities acquired (transferred) in connection with financial guarantee commutations (65) — June 30, 2024 2023 Reconciliation of cash, cash equivalents, and restricted cash reported within the Cash and cash equivalents $ 24 $ 33 Restricted cash 11 10 Variable Interest Entity restricted cash 62 266 Total cash, cash equivalents, and restricted cash shown on the Consolidated Statements of Cash Flows $ 97 $ 309 Restricted cash is cash that we do not have the right to use for general purposes and includes fiduciary cash held by Ambac's insurance distribution subsidiaries, consolidated variable interest entity cash to support the obligations of the consolidated VIEs and cash received as collateral under their derivatives agreements. Reclassifications and Rounding Reclassifications may have been made to prior years' amounts to conform to the current year's presentation. Certain amounts and tables in the consolidated financial statements and associated notes may not add due to rounding. Adopted Accounting Standards There have been no new accounting standards adopted during 2024. Future Application of Accounting Standards and Required Disclosures Segment Reporting In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280) - Improvement to Reportable Segment Disclosures . The ASU requires disclosure of the following: • Significant segment expenses regularly provided to the chief operating decision maker (CODM) and included within the reported measure(s) of a segment’s profit or loss. • The amount and composition of "other segment items." This amount reconciles segment revenue, less significant expenses, to the reported measure(s) of a segment’s profit or loss. • The CODM's title and position. • How the CODM uses the reported measure(s) of a segment’s profit or loss to assess segment performance and decide how to allocate resources. • All segment profit or loss and assets disclosures currently required annually by Topic 280, as well as those introduced by the ASU, to also be disclosed in interim periods. The ASU also permits a public entity to report multiple measures of a segment’s profit or loss as long as: i) all the reported measures of a segment’s profit or loss are used by the CODM for purposes of assessing performance and allocating resources and ii) the measure closest to GAAP is also provided. The ASU is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. Ambac will adopt this ASU for the annual reporting period ending December 31, 2024 and we are evaluating its impact on Ambac's financial statements. Income Taxes In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures . The enhancements in the ASU include the following: • Within the rate reconciliation table, disclosure of additional categories of information about federal, state and foreign income taxes and providing more details about the reconciling items in some categories if the items meet a quantitative threshold. • Annual disclosure of income taxes paid (net of refunds received) disaggregated by federal (national), state and foreign taxes and disaggregation of the information by jurisdiction based on a quantitative threshold. • Other disclosures include: i) income (or loss) from continuing operations before income tax expense (or benefit) disaggregated between domestic and foreign and ii) income tax expense (or benefit) from continuing operations disaggregated by federal (national), state, and foreign. The ASU is effective for annual periods beginning after December 15, 2024, with early adoption permitted. Ambac will adopt this ASU on January 1, 2025 and we are evaluating its impact on Ambac's financial statements.
Noncontrolling Interest Disclosure		Redeemable Noncontrolling Interest The Riverton, All Trans, Capacity Marine and Xchange acquisitions resulted in a majority ownership of the acquired entities by Ambac. Under the terms of all the acquisition agreements, Ambac has call options to purchase the remaining interests from the minority owners (i.e., noncontrolling interests) and the minority owners have put options to sell their interests to Ambac. Because the exercise of the put options are outside the control of Ambac, in accordance with the Distinguishing Liabilities from Equity Topic of the ASC, Ambac reports redeemable noncontrolling interests in the mezzanine section of its consolidated balance sheet. The redeemable noncontrolling interest is remeasured each period as the greater of: i. the carrying value under ASC 810, which attributes a portion of consolidated net income (loss) to the redeemable noncontrolling interest, and ii. the redemption value of the put option under ASC 480 as if it were exercisable at the end of the reporting period. Any increase (decrease) in the carrying amount of the redeemable noncontrolling interest as a result of adjusting to the redemption value of the put option is recorded as an offset to retained earnings. The impact of such differences on earnings per share are presented in Note 11. Net Income Per Share . Following is a rollforward of redeemable noncontrolling interest. Six Months Ended June 30, 2024 2023 Beginning balance $ 17 $ 20 Fair value of redeemable noncontrolling interest at acquisition date — — Net income attributable to redeemable noncontrolling interest (ASC 810) 1 1 Distributions (1) (1) Adjustment to redemption value (ASC 480) — — Ending balance $ 17 $ 20
Business Combination Disclosure		Acquisition of Beat Capital Partners Limited ("Beat") On June 4, 2024, the Company, entered into a share purchase agreement (the “Beat Purchase Agreement”), by and among the Company, Cirrata V LLC, a Delaware limited liability company and an indirect wholly owned subsidiary of AFG (the “Purchaser”), certain sellers set forth therein (the “Sellers”) and Beat, pursuant to which, effective July 31, 2024, the Purchaser purchased from the Sellers approximately 60% of the entire issued share capital of Beat for total consideration, as of the closing date, of approximately $278, of which approximately $249 was paid in cash and the remainder of which was satisfied through the issuance of 2,216,023 shares of AFG common stock to certain Sellers (the "Beat Transaction"). Beat’s management team and Bain Capital Credit LP (“Bain” and, together with certain members of Beat’s management team, the “Rollover Shareholders”) each retained approximately 20% of Beat’s issued share capital immediately after closing. AFG guaranteed the Purchaser’s performance under the Beat Purchase Agreement and the Shareholders’ Agreement (as defined below). AFG issued the common stock free and clear of any liens or restrictions (other than those arising under state and federal securities laws of the United States) and bearing a restrictive legend. The common stock has not been registered under the Securities Act in reliance upon an exemption from registration pursuant to Section 4(a)(2) of the Securities Act. AFG funded the cash portion of the consideration with a combination of available cash, approximately $65 of funding from AAC, and $150 of new indebtedness (the "Credit Facility") that was issued in the third quarter of 2024. Funding received from AAC and the Credit Facility are required to be repaid upon closing of the sale of AAC. To reduce its exposure to appreciation of the British Pound Sterling ("GBP") relative to the U.S. Dollar ("USD"), AFG entered into a foreign exchange futures contract under which it agreed to purchase an amount of GBP sufficient to cover the cash portion of the purchase price of Beat along with estimated GBP denominated expenses at an exchange rate of 1.2662 per USD. At the closing of the Beat Transaction, AFG entered into a Shareholders’ Agreement by and among AFG, the Purchaser, the Rollover Shareholders and Beat (the “Shareholders’ Agreement”).

Segment Reporting

Segment Reporting	6 Months Ended
	Jun. 30, 2024
Segment Reporting [Abstract]
Segment Reporting Disclosure	2. SEGMENT INFORMATION The Company reports its results of operations in three segments: Legacy Financial Guarantee Insurance, Specialty Property and Casualty Insurance and Insurance Distribution, separate from Corporate and Other, which is consistent with the manner in which the Company's chief operating decision maker ("CODM") reviews the business to assess performance and allocate resources. See Note 1. Business and Basis of Presentation for a description of each of the Company's business segments. The following tables summarize the components of the Company’s total revenues and expenses, pretax income (loss) and total assets by reportable business segment. Information provided below for “Corporate and Other” primarily relates to the operations of AFG, which will include investment income on its investment portfolio and costs to maintain the operations of AFG, including public company reporting, capital management and business development costs for the acquisition and development of new business initiatives. Three Months Ended June 30, 2024 Three Months Ended June 30, 2023 Legacy Financial Guarantee Insurance Specialty Property & Casualty Insurance Insurance Distribution Corporate & Other Consoli-dated (2) Legacy Financial Guarantee Insurance Specialty Property & Casualty Insurance Insurance Distribution Corporate & Other Consoli-dated (2) Revenues: Net premiums earned $ 6 $ 27 $ 33 $ 8 $ 8 $ 15 Commission income $ 13 13 $ 10 10 Program fees 3 3 2 2 Net investment income 32 1 — $ 2 36 32 1 — $ 2 35 Net investment gains (losses), including impairments (1) — 5 4 (3) — — (3) Net gains (losses) on derivative contracts 1 — — 1 — — Other (1) 16 — — — 15 2 — — — 3 Total revenues (2) 53 32 13 6 105 39 11 10 2 62 Expenses: Losses and loss adjustment expenses (benefit) (5) 23 18 2 6 7 Amortization of deferred acquisition costs, net — 5 5 — 1 1 Commission expenses 8 8 6 6 General and administrative expenses (3) 22 5 3 17 47 23 4 2 6 36 Depreciation expense (3) — — — — 1 — — — — — Intangible amortization 7 1 8 6 1 7 Interest expense 16 16 16 16 Total expenses (2) 40 33 12 17 103 47 11 9 6 73 Pretax income (loss) $ 13 $ (1) $ 1 $ (11) $ 2 $ (8) $ — $ 1 $ (4) $ (11) Total assets (2) $ 7,100 $ 713 $ 155 $ 216 $ 8,184 $ 7,376 $ 395 $ 137 $ 225 $ 8,132 Six Months Ended June 30, 2024 Six Months Ended June 30, 2023 Legacy Financial Guarantee Insurance Specialty Property & Casualty Insurance Insurance Distribution Corporate & Other Consoli-dated (2) Legacy Financial Guarantee Insurance Specialty Property & Casualty Insurance Insurance Distribution Corporate & Other Consoli-dated (2) Revenues: Net premiums earned $ 13 $ 53 $ 66 $ 14 $ 15 $ 29 Commission income $ 31 $ 31 $ 25 $ 25 Program fees $ 6 $ 6 $ 4 $ 4 Net investment income (loss) $ 70 $ 3 $ — $ 4 $ 78 $ 63 $ 2 $ 4 $ 69 Net investment gains (losses), including impairments $ — $ — $ 5 $ 4 $ (8) $ — $ — $ (8) Net gains (losses) on derivative contracts $ 2 $ — $ 2 $ (3) $ — $ (3) Other (1) $ 21 $ — $ — $ — $ 21 $ 4 $ — $ — $ — $ 4 Total revenues (2) $ 107 $ 61 $ 31 $ 8 $ 207 $ 71 $ 20 $ 25 $ 4 $ 120 Expenses: Losses and loss adjustment expenses $ (26) $ 42 $ 16 $ 15 $ 10 $ 25 Amortization of deferred acquisition costs, net $ — $ 10 $ 10 $ — $ 3 $ 3 Commission expenses $ 18 $ 18 $ 14 $ 14 General and administrative expenses (3) $ 44 $ 8 $ 6 $ 24 $ 82 $ 52 $ 8 $ 5 $ 7 $ 72 Depreciation expense (3) $ — $ — $ — $ 1 $ 1 $ 1 $ — $ — $ — $ 1 Intangible amortization $ 18 $ 2 $ 21 $ 11 $ 2 $ 13 Interest expense $ 32 $ 32 $ 32 $ 32 Total expenses (2) $ 69 $ 61 $ 26 $ 24 $ 180 $ 111 $ 21 $ 20 $ 8 $ 160 Pretax income (loss) $ 38 $ 1 $ 5 $ (16) $ 27 $ (40) $ (1) $ 4 $ (3) $ (40) (1) Other revenues include the following line item on the Consolidated Statements of Total Comprehensive Income: Income (loss) on variable interest entities and other income. (2) Inter-segment revenues and inter-segment pre-tax income (loss) amounts are insignificant and are not presented separately. (3) The Consolidated Statements of Comprehensive Income presents the sum of these items as General & Administrative Expenses.

Investments

Investments	6 Months Ended
	Jun. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Investments	3. INVESTMENTS Ambac’s non-VIE invested assets are primarily comprised of fixed maturity securities classified as either available-for-sale or trading securities, and interests in pooled investment funds, which are reported within Other investments on the Consolidated Balance Sheets. Interests in pooled investment funds in the form of common stock or in-substance common stock are classified as trading securities, while limited partner interests in such funds are reported using the equity method. Fixed maturity securities classified as trading are unrated municipal bond obligations of Puerto Rico issuing entities that are part of the the PROMESA restructuring process as described further in the Notes to Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023 . Fixed Maturity Securities: The amortized cost and estimated fair value of available-for-sale investments, excluding VIE investments, at June 30, 2024 and December 31, 2023, were as follows: June 30, 2024: December 31, 2023: Amortized Allowance for Credit Losses (2) Gross Unrealized Estimated Amortized Allowance for Credit Losses Gross Unrealized Estimated Gains Losses Gains Losses Fixed maturity securities: Municipal obligations $ 71 $ — $ 1 $ 2 $ 71 $ 72 — $ 1 $ 1 $ 72 Corporate obligations 786 — 2 46 742 785 — 4 44 745 Foreign obligations 111 — — 7 105 105 — 1 6 100 U.S. government obligations 108 — — 4 105 85 — 1 4 82 Residential mortgage-backed securities 240 3 28 13 253 239 3 28 14 250 Commercial mortgage-backed securities 46 — — — 46 19 — — — 19 Collateralized debt obligations 141 — 1 — 141 139 — 1 1 139 Other asset-backed securities (1) 234 — 12 5 241 301 — 3 1 303 1,737 3 45 77 1,703 1,744 3 40 71 1,710 Short-term 314 — — — 314 426 — — — 426 2,051 3 45 77 2,017 2,170 3 40 71 2,135 Fixed maturity securities pledged as collateral: U.S. government obligations 27 — — 1 25 — — — — — Short-term — — — — — 27 — — — 27 27 — — 1 25 27 — — — 27 Total available-for-sale investments $ 2,078 $ 3 $ 45 $ 78 $ 2,043 $ 2,197 3 $ 40 $ 71 $ 2,162 (1) Consists primarily of military housing and student loan securities. (2) For the three and six months ended June 30, 2024, the allowance for credit losses changed by $0 on residential mortgage-backed securities for which credit losses were not previously recorded. The amortized cost and estimated fair value of available-for-sale investments, excluding VIE investments, at June 30, 2024, by contractual maturity, were as follows: Amortized Estimated Due in one year or less $ 439 $ 437 Due after one year through five years 543 521 Due after five years through ten years 304 279 Due after ten years 132 124 1,418 1,361 Residential mortgage-backed securities 240 253 Commercial mortgage-backed securities 46 46 Collateralized debt obligations 141 141 Other asset-backed securities 234 241 Total $ 2,078 $ 2,043 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 on Fixed Maturity Securities: The following table shows gross unrealized losses and fair values of Ambac’s available-for-sale investments, excluding VIE investments, which at June 30, 2024 and December 31, 2023, did not have an allowance for credit losses This information is aggregated by investment category and length of time that the individual securities have been in a continuous unrealized loss position, at June 30, 2024 and December 31, 2023: June 30, 2024 December 31, 2023 Less Than 12 Months 12 Months or More Total Less Than 12 Months 12 Months or More Total Fair Gross Fair Gross Fair Gross Fair Gross Fair Gross Fair Gross Fixed maturity securities: Municipal obligations $ 21 $ — $ 15 $ 1 $ 35 $ 2 $ 7 $ — $ 16 $ 1 $ 23 $ 1 Corporate obligations 125 3 493 43 618 46 75 2 509 43 584 44 Foreign obligations 25 — 55 7 80 7 8 — 56 6 64 6 U.S. government obligations 58 1 37 3 95 4 27 1 37 2 63 4 Residential mortgage-backed securities 16 — 113 13 129 13 6 — 98 14 104 14 Commercial mortgage-backed securities 17 — — — 17 — 3 — — — 3 — Collateralized debt obligations 18 — 3 — 22 — 1 — 93 1 95 1 Other asset-backed securities 45 1 72 4 117 5 57 1 35 1 92 1 326 5 787 71 1,113 77 184 4 844 68 1,028 71 Short-term 46 — — — 46 — 4 — — — 4 — 372 5 787 71 1,159 77 187 4 844 68 1,032 71 U. S. government obligations 25 1 — — 25 1 — — — — — — Total collateralized investments 25 1 — — 25 1 — — — — — — Total temporarily impaired securities $ 398 $ 7 $ 787 $ 71 $ 1,184 $ 78 $ 187 $ 4 $ 844 $ 68 $ 1,032 $ 71 Management has determined that the securities in the above table do not have credit impairment as of June 30, 2024 and December 31, 2023, based upon (i) no actual or expected principal and interest payment defaults on these securities; (ii) analysis of the creditworthiness of the issuer and financial guarantor, as applicable, and (iii) for debt securities that are non-highly rated beneficial interests in securitized financial assets, analysis of whether there was an adverse change in projected cash flows. Management's evaluation as of June 30, 2024, includes the expectation that all principal and interest payments on securities guaranteed by AAC or Ambac UK will be made timely and in full. Ambac’s assessment about whether a security is credit impaired reflects management’s current judgment regarding facts and circumstances specific to the security and other factors. If that judgment changes, Ambac may record a charge for credit impairment in future periods. The declines in fair value and resultant unrealized losses across asset classes as of June 30, 2024, included in the above table resulted from the impact of increasing interest rates and market spreads. Management has determined that the securities with unrealized losses are not credit impaired. Further discussion of management's assessment with respect to security categories with larger unrealized loss balances is below. Corporate obligations The gross unrealized losses on corporate obligations as of June 30, 2024, resulted primarily from an increase in interest rates since the securities were purchased. Unrealized losses of $45 related to 733 investment grade securities with an average unrealized loss equal to 7% of amortized cost at June 30, 2024. Securities that have below investment grade credit ratings or are unrated comprise less than a million of the gross unrealized loss and have an average unrealized loss equal to 8% of amortized cost at June 30, 2024. Management believes that the full and timely receipt of all principal and interest payment on corporate obligations with unrealized losses as of June 30, 2024, is probable. Residential mortgage-backed securities and Other asset-backed securities As of June 30, 2024, $13 of the unrealized loss on residential mortgage-backed securities related to 15 Ambac insured securities. Five of these account for $13 of the unrealized loss and have an average unrealized loss equal to 12% of amortized cost. The $5 unrealized loss on other asset backed securities related primarily to 13 Ambac-insured securities that have an average unrealized loss equal to 5% of amortized cost. The majority of these unrealized losses for both residential mortgage-backed and other asset-backed securities relate to securities with long dated weighted average lives making their fair values sensitive to interest rate changes. Also, most of these securities have below investment grade credit ratings or are unrated. The unrealized losses on these obligations resulted from adverse market conditions for long dated credit assets. As noted above, expected cash flows used in evaluating credit impairment of Ambac-insured securities contemplate full and timely payment of all principal and interest payments. This assumption is included in the projection of model based cash flows used in evaluating credit impairments on beneficial interests in securitized financial assets, including the residential mortgage backed and student loan asset backed securities included in this group. Investment Income (Loss) Net investment income (loss) was comprised of the following for the affected periods: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Fixed maturity securities $ 22 $ 19 $ 45 $ 35 Short-term investments 5 5 10 10 Investment expense (1) (1) (3) (3) Securities available-for-sale and short-term 26 22 52 43 Fixed maturity securities - trading 2 4 4 5 Other investments 8 9 21 22 Total net investment income (loss) $ 36 $ 35 $ 78 $ 69 Net investment income (loss) from Other investments primarily represents changes in fair value on equity securities, including certain pooled investment funds, and income from investment limited partnerships and other equity interests accounted for under the equity method. Net Investments Gains (Losses), including Impairments: The following table details amounts included in net investment gains (losses) and impairments included in earnings for the affected periods: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Gross realized gains on securities $ 7 $ — $ 7 $ 1 Gross realized losses on securities (1) (2) (1) (3) Foreign exchange gains (losses) (1) (2) — (4) Credit impairments (2) — (1) (1) Intent / requirement to sell impairments — — — — Net investment gains (losses), including impairments $ 4 $ (3) $ 4 $ (8) Ambac had an allowance for credit losses of $3 and $1 at June 30, 2024 and 2023, respectively. Ambac did not purchase any financial assets with credit deterioration for the three and six months ended June 30, 2024 and 2023. Counterparty Collateral, Deposits with Regulators and Other Restrictions: Ambac routinely pledges and receives collateral related to certain transactions. Securities held directly in Ambac’s investment portfolio with a fair value of $25 and $27 at June 30, 2024 and December 31, 2023, respectively, were pledged to derivative counterparties. Ambac’s derivative counterparties have the right to re-pledge the investment securities and as such, these pledged securities are separately classified on the Consolidated Balance Sheets as either "Fixed maturity securities pledged as collateral, at fair value" or "Short-term investments pledged as collateral, at fair value." Refer to Note 6. Derivative Instruments for further information on cash collateral. There was no cash or securities received from other counterparties that were re-pledged by Ambac. Securities carried at $29 and $24 at June 30, 2024 and December 31, 2023, respectively, were deposited by Ambac's insurance subsidiaries with governmental authorities or designated custodian banks as required by laws affecting insurance companies. Invested assets carried at $1 and $1 at June 30, 2024 and December 31, 2023, were deposited as security in connection with a letter of credit issued for an office lease. Fiduciary funds held by Ambac's insurance distribution subsidiaries, carried at $2 and $2 at June 30, 2024 and December 31, 2023, respectively, are included in the invested assets. Guaranteed Securities: Ambac’s fixed maturity portfolio includes securities covered by guarantees issued by AAC or Ambac UK (“insured securities”). The following table represents the fair value and weighted-average underlying rating of insured securities in Ambac's investment portfolio at June 30, 2024 and December 31, 2023, respectively: June 30, 2024 December 31, 2023 Municipal obligations $ 8 $ 9 Mortgage-backed securities 244 240 Asset-backed securities 151 232 Total $ 403 482 Weighted average underlying rating B- B- (1) Ratings are based on the lower of Standard & Poor’s or Moody’s rating. If unavailable, Ambac’s internal rating is used. Other Investments: Ambac's investment portfolio includes interests in various pooled investment funds. Fair value and additional information about investments in pooled funds, by investment type, is summarized in the table below. Except as noted in the table, fair value as reported is determined using net asset value ("NAV") as a practical expedient. Redemption of certain funds valued using NAV may be subject to withdrawal limitations and/or redemption fees which vary with the timing and notification of withdrawal provided by the investor. In addition to these investments, Ambac has unfunded commitments of $30 to private credit and private equity funds at June 30, 2024. Fair Value Class of Funds June 30, December 31, 2023 Redemption Frequency Redemption Notice Period Hedge funds (1) $ 117 $ 112 quarterly or semi-annually 90 days Private credit (2) 83 84 quarterly if permitted 180 days if permitted High yields and leveraged loans (3) (10) 137 85 daily 0 - 30 days Equity market investments (4) (10) 40 38 daily 0 days Investment grade floating rate income (5) 53 52 weekly 0 days Private equity (6) 79 70 quarterly if permitted 90 days if permitted Real estate properties (7) — 21 see footnote (7) see footnote (7) Convertible bonds (8)(10) 23 — daily 0 days Insurance-linked investments (9) — 1 see footnote (9) see footnote (9) Total equity investments in pooled funds $ 533 $ 463 (1) This class seeks to generate superior risk-adjusted returns through selective asset sourcing, active trading and hedging strategies across a range of asset types. (2) This class aims to obtain high long-term returns primarily through credit and preferred equity investments with low liquidity and defined term. (3) This class of funds includes investments in a range of instruments including high-yield bonds, leveraged loans, CLOs, ABS and floating rate notes to generate income and capital appreciation. (4) This class of funds aim to achieve long term growth through diversified exposure to global equity-markets. (5) This class of funds includes investments in high quality floating rate debt securities including ABS and corporate floating rate notes. (6) This class seeks to generate long-term capital appreciation through investments in private equity, equity-related and other instruments. (7) Investments consisted of UK property to generate income and capital growth. The fund in which Ambac was invested has terminated on May 30, 2024 and is in the process of distributing remaining capital. Amounts owed Ambac from the fund are included in Other assets on the Consolidated Balance Sheet as of June 30, 2024. (8) This class seeks to generate total returns from portfolios focused primarily on convertible securities. (9) This class seeks to generate returns from insurance markets through investments in catastrophe bonds, life insurance and other insurance linked investments. This investment was restricted in connection with the unwind of certain insurance linked exposures. Ambac's investment was fully redeemed by March 31, 2024. (10) These categories include fair value amounts totaling $153 and $77 at June 30, 2024 and December 31, 2023, respectively, that are readily determinable and are priced through pricing vendors, including for Equity market investments $40 and $38, High yield and leveraged loans products $89 and $39, and Convertible bonds investments $23 and $0.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. 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 has three broad levels as follows: l Level 1 Quoted prices for identical instruments in active markets. Assets and liabilities classified as Level 1 include US Treasury and foreign government obligations traded in highly liquid and transparent markets, certain highly liquid pooled fund investments, exchange traded futures contracts and money market funds. l 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 maturity securities representing municipal, asset-backed and corporate obligations, certain interest rate swap contracts and most long-term debt of variable interest entities consolidated under the Consolidation Topic of the ASC. l 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 certain uncollateralized interest rate swap contracts and certain investments in fixed maturity securities. Additionally, Level 3 assets and liabilities generally include loan receivables, and certain long-term debt of variable interest entities consolidated under the Consolidation Topic of the ASC. The Fair Value Measurement Topic of the ASC permits, as a practical expedient, the estimation of fair value of certain investments in funds using the net asset value per share of the investment or its equivalent (“NAV”). Investments in funds valued using NAV are not categorized as Level 1, 2 or 3 under the fair value hierarchy. The Investments — Equity Securities Topic of the ASC permits the measurement of certain equity securities without a readily determinable fair value at cost, less impairment, and adjusted to fair value when observable price changes in identical or similar investments from the same issuer occur (the "measurement alternative"). The fair values of investments measured under this measurement alternative are not included in the below disclosures of fair value of financial instruments. The following table sets forth the carrying amount and fair value of Ambac’s financial assets and liabilities as of June 30, 2024 and December 31, 2023, 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. June 30, 2024 December 31, 2023 Carrying Total Fair Fair Value Measurements Categorized as: Carrying Total Fair Fair Value Measurements Categorized as: Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Financial assets: Fixed maturity securities: Municipal obligations $ 101 $ 101 $ — $ 101 $ — $ 99 $ 99 $ — $ 99 $ — Corporate obligations 742 742 — 742 — 745 745 — 726 19 Foreign obligations 105 105 105 — — 100 100 100 — — U.S. government obligations 105 105 105 — — 82 82 82 — — Residential mortgage-backed securities 253 253 — 253 — 250 250 — 250 — Commercial mortgage-backed securities 46 46 — 46 — 19 19 — 19 — Collateralized debt obligations 141 141 — 141 — 139 139 — 139 — Other asset-backed securities 241 241 — 164 77 303 303 — 235 68 Fixed maturity securities, pledged as collateral: U.S. government obligations 25 25 25 — — — — — — — Short-term — — — — — 27 27 27 — — Short term investments 314 314 313 1 — 426 426 421 5 — Other investments (1) 558 533 153 — — 475 463 77 — — Cash, cash equivalents and restricted cash 35 35 35 — — 28 28 27 2 — Other assets - Derivatives: Interest rate swaps—asset position 18 18 — — 18 25 25 — — 25 Warrants 1 1 — — 1 1 1 — — 1 Other assets-Loans 2 1 — — 1 2 2 — — 2 Variable interest entity assets: Fixed maturity securities: Corporate obligations, fair value option 2,010 2,010 — — 2,010 2,072 2,072 — — 2,072 Fixed maturity securities: Municipal obligations, available-for-sale 91 91 — 91 — 95 95 — 95 — Restricted cash 62 62 62 — — 246 246 246 — Loans 1,567 1,567 — — 1,567 1,663 1,663 — — 1,663 Derivative assets: Interest rate swaps—asset position 174 174 — 174 — 190 190 — 190 — Derivative assets: Currency swaps—asset position 34 34 — 34 — 36 36 — 36 — Total financial assets $ 6,626 $ 6,600 $ 797 $ 1,748 $ 3,675 $ 7,022 $ 7,010 $ 979 $ 1,795 $ 3,850 Financial liabilities: Long term debt, including accrued interest $ 1,015 $ 772 $ — $ 753 $ 19 $ 983 $ 697 $ — $ 679 $ 18 Other liabilities - Derivatives: Interest rate swaps—liability position 25 25 — 25 — 35 35 — 35 — FX forward — — — — — — — — — — Liabilities for net financial guarantees written (2) 229 488 — — 488 292 788 — — 788 Variable interest entity liabilities: Long-term debt 2,853 2,852 — 2,646 205 2,967 2,980 — 2,760 220 Derivative liabilities: Interest rate swaps—liability position 1,136 1,136 — 1,136 — 1,197 1,197 — 1,197 — Total financial liabilities $ 5,258 $ 5,273 $ — $ 4,561 $ 712 $ 5,474 $ 5,697 $ — $ 4,671 $ 1,026 (1) Excluded from the fair value measurement categories in the table above are investment funds of $380 and $386 as of June 30, 2024 and December 31, 2023, respectively, which are measured using NAV as a practical expedient. Also excluded from the fair value amounts in the table above are equity securities with a carrying value of $26 and $13 as of June 30, 2024 and December 31, 2023, respectively, that do not have readily determinable fair values and have carrying amounts determined using the measurement alternative. (2) The carrying value of net financial guarantees written includes financial guarantee amounts in 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. The determination of fair value for financial instruments categorized in Level 2 or 3 involves 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 values for financial instruments. 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 maturity securities, equity interests in pooled investment funds, derivative instruments and certain variable interest entity assets and liabilities. 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 to validate fair value model results. However, financial instruments valued using significant unobservable inputs typically 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. Fixed Maturity Securities: The fair values of fixed maturity investment securities are based primarily on market prices received from broker quotes or alternative pricing sources. Because many fixed maturity securities do not trade on a daily basis, pricing sources apply available market information through processes such as matrix pricing to calculate fair value. Such prices generally consider a variety of factors, including recent trades of the same and similar securities. In those cases, the items are classified within Level 2. For those fixed maturity 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. 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. 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. At June 30, 2024, approximately 2%, 94% and 4% of the fixed maturity investment portfolio (excluding variable interest entity investments) was valued using broker quotes, alternative pricing sources and internal valuation models, respectively. At December 31, 2023, approximately 2%, 94% and 4% of the fixed maturity investment portfolio (excluding variable interest entity investments) was valued using broker quotes, alternative pricing sources and internal valuation models, respectively. Ambac performs various review and validation procedures to quoted and modeled prices for fixed maturity securities, including price variance analyses, missing and static price reviews, overall valuation analysis by portfolio managers 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), internally modeled prices and/or other relevant data, 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 portfolio managers and finance managers. Information about the valuation inputs for fixed maturity securities classified as Level 3 is included below: Other asset-backed securities: This security is a subordinated tranche of a securitization collateralized by Ambac-insured military housing bonds. The fair value classified as Level 3 was $77 and $68 at June 30, 2024 and December 31, 2023, respectively. Fair value was calculated using a discounted cash flow approach with expected future cash flows discounted using a yield consistent with the security type and rating. Significant inputs for the valuation at June 30, 2024 and December 31, 2023 include the following: June 30, December 31, 2023: a. Coupon rate: 5.98% 5.97% b. Average Life: 12.47 years 12.80 years c. Yield: 10.00% 12.00% Corporate obligations: This includes certain investments in convertible debt securities. The fair value classified as Level 3 was $0 and $19 at June 30, 2024 and December 31, 2023, respectively. Fair value was calculated by discounting cash flows with weighted average maturity of 0.89 years and yield of 11.2% at December 31, 2023. Yields used are consistent with the security type and rating. Other Investments: Other investments primarily relate to investments in pooled investment funds. The fair value of pooled investment funds is determined using dealer quotes or alternative pricing sources when such investments have readily determinable fair values. When fair value is not readily determinable, pooled investment funds are valued using NAV as a practical expedient as permitted under the Fair Value Measurement Topic of the ASC. Refer to Note 3. Investments for additional information about such investments in pooled funds that are reported at fair value using NAV as a practical expedient. Derivative Instruments: Ambac’s derivative instruments primarily comprise interest rate swaps and exchange traded futures contracts (terminated during the second quarter of 2023). 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 yield curves. The valuation of certain derivative contracts may 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 derivative liabilities. Factors considered in estimating the amount of any Ambac credit valuation adjustment ("CVA") on such contracts include collateral posting provisions, right of set-off with the counterparty, the period of time remaining on the derivative and the pricing of recent terminations. The aggregate Ambac CVA impact was not significant to the fair value of derivatives at June 30, 2024 or December 31, 2023. Interest rate swaps that are not centrally cleared are valued using vendor-developed models that incorporate interest rates and yield curves that are observable and regularly quoted. These models provide the net present value of the derivatives based on contractual terms and observable market data. Generally, the need for counterparty (or Ambac) CVAs on interest rate derivatives is mitigated by the existence of collateral posting agreements under which adequate collateral has been posted. Certain of these 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 determination of their fair value. Ambac holds warrants to purchase equity shares of development stage companies. These warrants have a fair value of $1 and $1 as of June 30, 2024 and December 31, 2023, respectively. Fair value was determined using a standard warrant valuation model with internally developed input assumptions. Financial Guarantees: Fair value of net financial guarantees written represents our estimate of the cost to Ambac to completely transfer its insurance obligation to another market participant of comparable credit worthiness. In theory, this amount should be the same amount that another market participant of comparable credit worthiness would hypothetically charge in the marketplace, on a present value basis, to provide the same protection as of the balance sheet date. This fair value estimate of financial guarantees is presented on a net basis and includes direct and assumed contracts written, net of ceded reinsurance contracts. Long-term Debt: Long-term debt includes AAC surplus notes and the Ambac UK debt issued in connection with a policy commutation. The fair values of surplus notes is based on prices received from third-party sources and are classified as Level 2. The fair value of Ambac UK debt estimated based upon internal valuation models and is classified as Level 3. Other Financial Assets and Liabilities: Included in Other assets are loans, the fair values of which are estimated based upon internal valuation models and are classified as Level 3. Variable Interest Entity Assets and Liabilities: The financial assets and liabilities of Legacy Financial Guarantee Insurance VIEs ("FG VIEs") consolidated under the Consolidation Topic of the ASC consist primarily of fixed maturity securities and loans held by the VIEs, derivative instruments and notes issued by the VIEs which are reported as long-term debt. As described in Note 8. Variable Interest Entities , these FG VIEs are securitization entities which have liabilities and/or assets guaranteed by AAC or Ambac UK. The fair values of FG VIE long-term debt are based on price quotes received from independent market sources when available. Such quotes are considered Level 2 and generally consider a variety of factors, including recent trades of the same and similar securities. For those instruments where quotes were not available or cannot be reasonably corroborated, fair values are based on internal valuation models. Comparable to the sensitivities of investments in fixed maturity securities described above, longer (shorter) expected maturities or higher (lower) yields used in the valuation model will, in isolation, result in decreases (increases) in fair value liability measurement for FG VIE long-term debt. FG VIE derivative asset and liability fair values are determined using vendor-developed valuation models, which incorporated observable market data related to specific derivative contractual terms including interest rates, foreign exchange rates and yield curves. The fair value of FG VIE fixed maturity securities and loan assets are generally based on Level 2 market price quotes received from independent market sources when available. When FG VIE asset fair values are not readily available from market quotes, values are estimated internally. Internal valuations of FG VIE’s fixed maturity securities or loan assets are derived from the fair values of the notes issued by the respective VIE and the VIE’s derivatives, determined as described above, adjusted for the fair values of Ambac’s financial guarantees associated with the VIE. The fair value of financial guarantees consist of: (i) estimated future premium cash flows discounted at a rate consistent with that implicit in the fair value of the VIE’s liabilities and (ii) estimates of future claim payments discounted at a rate that includes Ambac’s own credit risk. Estimated future premium payments to be paid by the VIEs were discounted at a weighted average rate of 6.6% and 6.3% at June 30, 2024 and December 31, 2023, respectively. At June 30, 2024, the range of these discount rates was between 5.8% and 8.2%. At December 31, 2023, the range of these discount rates were between 5.3% and 7.8%. Additional Fair Value Information for Financial Assets and Liabilities Accounted for at Fair Value: The following tables present the changes in the Level 3 fair value category for the periods presented in 2024 and 2023. 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 Investments Derivatives Investments Loans Total Three Months Ended June 30, 2024: Balance, beginning of period $ 87 $ 21 $ 2,070 $ 1,604 $ 3,782 Total gains/(losses) realized and unrealized: Included in earnings 7 (3) (51) 29 (19) Included in other comprehensive income 9 — 3 3 15 Settlements (26) — (12) (68) (106) Balance, end of period $ 77 $ 18 $ 2,010 $ 1,567 $ 3,672 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 $ 7 $ (3) $ (51) $ 29 $ (19) The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 9 $ — $ 3 $ 3 $ 15 Three Months Ended June 30, 2023: Balance, beginning of period $ 81 $ 31 $ 2,003 $ 1,856 $ 3,972 Total gains/(losses) realized and unrealized: Included in earnings — (5) (53) (66) (124) Included in other comprehensive income — — 14 50 64 Settlements — — (12) (69) (81) Balance, end of period $ 81 $ 25 $ 1,952 $ 1,772 $ 3,831 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 $ — $ (5) $ (53) $ (66) $ (124) The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ — $ — $ 14 $ 50 $ 64 Level 3 - Financial Assets and Liabilities Accounted for at Fair Value VIE Assets Investments Derivatives Investments Loans Total Six Months Ended June 30, 2024: Balance, beginning of period $ 87 $ 26 $ 2,072 $ 1,663 $ 3,848 Additions of VIEs consolidated — Total gains/(losses) realized and unrealized: Included in earnings 7 (8) (32) 49 16 Included in other comprehensive income 9 — (18) (14) (23) Purchases — — — — — Settlements (27) — (12) (132) (170) Balance, end of period $ 77 $ 18 $ 2,010 $ 1,567 $ 3,672 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 $ 7 $ (8) $ (32) $ 49 $ 16 The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 9 $ — $ (18) $ (14) $ (23) Six Months Ended June 30, 2023: Balance, beginning of period $ 79 $ 26 $ 1,828 $ 1,829 $ 3,762 Additions of VIEs consolidated — — — — — Total gains/(losses) realized and unrealized: Included in earnings 1 — 80 (7) 73 Included in other comprehensive income 3 — 57 92 152 Purchases — — — — — Settlements (1) — (12) (141) (155) Balance, end of period $ 81 $ 25 $ 1,952 $ 1,772 $ 3,831 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 $ — $ 80 $ (7) $ 73 The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 3 $ — $ 57 $ 92 152 Invested assets and VIE long-term debt are transferred into Level 3 when internal valuation models that include significant unobservable inputs are used to estimate fair value. All such securities that have internally modeled fair values have been classified as Level 3. Derivative instruments are transferred into Level 3 when the use of unobservable inputs becomes significant to the overall valuation. There were no transfers of financial instruments into or out of Level 3 in the periods disclosed. Gains and losses (realized and unrealized) relating to Level 3 assets and liabilities included in earnings for the affected periods are reported as follows: Three Months Ended June 30, 2024 Three Months Ended June 30, 2023 Net Net Gains Income (Loss) Other Net Net Gains Income (Loss) Other Total gains (losses) included in earnings for the period $ 7 $ (3) $ (22) $ — $ — $ (5) $ (119) $ — Changes in unrealized gains (losses) relating to financial instruments still held at the reporting date 9 (3) (22) — — (5) (119) — Six Months Ended June 30, 2024 Six Months Ended June 30, 2023 Net Net Gains Income (Loss) Other Net Net Gains Income (Loss) Other Total gains or losses included in earnings for the period $ 7 $ (8) $ 17 $ — $ 1 $ — $ 72 $ — Changes in unrealized gains or losses included in earnings relating to the assets and liabilities still held at the reporting date 9 (8) 17 — — — 72 —

Insurance Contracts

Insurance Contracts	6 Months Ended
	Jun. 30, 2024
Insurance [Abstract]
Fair Value Measurements	4. 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 has three broad levels as follows: l Level 1 Quoted prices for identical instruments in active markets. Assets and liabilities classified as Level 1 include US Treasury and foreign government obligations traded in highly liquid and transparent markets, certain highly liquid pooled fund investments, exchange traded futures contracts and money market funds. l 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 maturity securities representing municipal, asset-backed and corporate obligations, certain interest rate swap contracts and most long-term debt of variable interest entities consolidated under the Consolidation Topic of the ASC. l 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 certain uncollateralized interest rate swap contracts and certain investments in fixed maturity securities. Additionally, Level 3 assets and liabilities generally include loan receivables, and certain long-term debt of variable interest entities consolidated under the Consolidation Topic of the ASC. The Fair Value Measurement Topic of the ASC permits, as a practical expedient, the estimation of fair value of certain investments in funds using the net asset value per share of the investment or its equivalent (“NAV”). Investments in funds valued using NAV are not categorized as Level 1, 2 or 3 under the fair value hierarchy. The Investments — Equity Securities Topic of the ASC permits the measurement of certain equity securities without a readily determinable fair value at cost, less impairment, and adjusted to fair value when observable price changes in identical or similar investments from the same issuer occur (the "measurement alternative"). The fair values of investments measured under this measurement alternative are not included in the below disclosures of fair value of financial instruments. The following table sets forth the carrying amount and fair value of Ambac’s financial assets and liabilities as of June 30, 2024 and December 31, 2023, 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. June 30, 2024 December 31, 2023 Carrying Total Fair Fair Value Measurements Categorized as: Carrying Total Fair Fair Value Measurements Categorized as: Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Financial assets: Fixed maturity securities: Municipal obligations $ 101 $ 101 $ — $ 101 $ — $ 99 $ 99 $ — $ 99 $ — Corporate obligations 742 742 — 742 — 745 745 — 726 19 Foreign obligations 105 105 105 — — 100 100 100 — — U.S. government obligations 105 105 105 — — 82 82 82 — — Residential mortgage-backed securities 253 253 — 253 — 250 250 — 250 — Commercial mortgage-backed securities 46 46 — 46 — 19 19 — 19 — Collateralized debt obligations 141 141 — 141 — 139 139 — 139 — Other asset-backed securities 241 241 — 164 77 303 303 — 235 68 Fixed maturity securities, pledged as collateral: U.S. government obligations 25 25 25 — — — — — — — Short-term — — — — — 27 27 27 — — Short term investments 314 314 313 1 — 426 426 421 5 — Other investments (1) 558 533 153 — — 475 463 77 — — Cash, cash equivalents and restricted cash 35 35 35 — — 28 28 27 2 — Other assets - Derivatives: Interest rate swaps—asset position 18 18 — — 18 25 25 — — 25 Warrants 1 1 — — 1 1 1 — — 1 Other assets-Loans 2 1 — — 1 2 2 — — 2 Variable interest entity assets: Fixed maturity securities: Corporate obligations, fair value option 2,010 2,010 — — 2,010 2,072 2,072 — — 2,072 Fixed maturity securities: Municipal obligations, available-for-sale 91 91 — 91 — 95 95 — 95 — Restricted cash 62 62 62 — — 246 246 246 — Loans 1,567 1,567 — — 1,567 1,663 1,663 — — 1,663 Derivative assets: Interest rate swaps—asset position 174 174 — 174 — 190 190 — 190 — Derivative assets: Currency swaps—asset position 34 34 — 34 — 36 36 — 36 — Total financial assets $ 6,626 $ 6,600 $ 797 $ 1,748 $ 3,675 $ 7,022 $ 7,010 $ 979 $ 1,795 $ 3,850 Financial liabilities: Long term debt, including accrued interest $ 1,015 $ 772 $ — $ 753 $ 19 $ 983 $ 697 $ — $ 679 $ 18 Other liabilities - Derivatives: Interest rate swaps—liability position 25 25 — 25 — 35 35 — 35 — FX forward — — — — — — — — — — Liabilities for net financial guarantees written (2) 229 488 — — 488 292 788 — — 788 Variable interest entity liabilities: Long-term debt 2,853 2,852 — 2,646 205 2,967 2,980 — 2,760 220 Derivative liabilities: Interest rate swaps—liability position 1,136 1,136 — 1,136 — 1,197 1,197 — 1,197 — Total financial liabilities $ 5,258 $ 5,273 $ — $ 4,561 $ 712 $ 5,474 $ 5,697 $ — $ 4,671 $ 1,026 (1) Excluded from the fair value measurement categories in the table above are investment funds of $380 and $386 as of June 30, 2024 and December 31, 2023, respectively, which are measured using NAV as a practical expedient. Also excluded from the fair value amounts in the table above are equity securities with a carrying value of $26 and $13 as of June 30, 2024 and December 31, 2023, respectively, that do not have readily determinable fair values and have carrying amounts determined using the measurement alternative. (2) The carrying value of net financial guarantees written includes financial guarantee amounts in 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. The determination of fair value for financial instruments categorized in Level 2 or 3 involves 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 values for financial instruments. 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 maturity securities, equity interests in pooled investment funds, derivative instruments and certain variable interest entity assets and liabilities. 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 to validate fair value model results. However, financial instruments valued using significant unobservable inputs typically 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. Fixed Maturity Securities: The fair values of fixed maturity investment securities are based primarily on market prices received from broker quotes or alternative pricing sources. Because many fixed maturity securities do not trade on a daily basis, pricing sources apply available market information through processes such as matrix pricing to calculate fair value. Such prices generally consider a variety of factors, including recent trades of the same and similar securities. In those cases, the items are classified within Level 2. For those fixed maturity 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. 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. 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. At June 30, 2024, approximately 2%, 94% and 4% of the fixed maturity investment portfolio (excluding variable interest entity investments) was valued using broker quotes, alternative pricing sources and internal valuation models, respectively. At December 31, 2023, approximately 2%, 94% and 4% of the fixed maturity investment portfolio (excluding variable interest entity investments) was valued using broker quotes, alternative pricing sources and internal valuation models, respectively. Ambac performs various review and validation procedures to quoted and modeled prices for fixed maturity securities, including price variance analyses, missing and static price reviews, overall valuation analysis by portfolio managers 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), internally modeled prices and/or other relevant data, 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 portfolio managers and finance managers. Information about the valuation inputs for fixed maturity securities classified as Level 3 is included below: Other asset-backed securities: This security is a subordinated tranche of a securitization collateralized by Ambac-insured military housing bonds. The fair value classified as Level 3 was $77 and $68 at June 30, 2024 and December 31, 2023, respectively. Fair value was calculated using a discounted cash flow approach with expected future cash flows discounted using a yield consistent with the security type and rating. Significant inputs for the valuation at June 30, 2024 and December 31, 2023 include the following: June 30, December 31, 2023: a. Coupon rate: 5.98% 5.97% b. Average Life: 12.47 years 12.80 years c. Yield: 10.00% 12.00% Corporate obligations: This includes certain investments in convertible debt securities. The fair value classified as Level 3 was $0 and $19 at June 30, 2024 and December 31, 2023, respectively. Fair value was calculated by discounting cash flows with weighted average maturity of 0.89 years and yield of 11.2% at December 31, 2023. Yields used are consistent with the security type and rating. Other Investments: Other investments primarily relate to investments in pooled investment funds. The fair value of pooled investment funds is determined using dealer quotes or alternative pricing sources when such investments have readily determinable fair values. When fair value is not readily determinable, pooled investment funds are valued using NAV as a practical expedient as permitted under the Fair Value Measurement Topic of the ASC. Refer to Note 3. Investments for additional information about such investments in pooled funds that are reported at fair value using NAV as a practical expedient. Derivative Instruments: Ambac’s derivative instruments primarily comprise interest rate swaps and exchange traded futures contracts (terminated during the second quarter of 2023). 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 yield curves. The valuation of certain derivative contracts may 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 derivative liabilities. Factors considered in estimating the amount of any Ambac credit valuation adjustment ("CVA") on such contracts include collateral posting provisions, right of set-off with the counterparty, the period of time remaining on the derivative and the pricing of recent terminations. The aggregate Ambac CVA impact was not significant to the fair value of derivatives at June 30, 2024 or December 31, 2023. Interest rate swaps that are not centrally cleared are valued using vendor-developed models that incorporate interest rates and yield curves that are observable and regularly quoted. These models provide the net present value of the derivatives based on contractual terms and observable market data. Generally, the need for counterparty (or Ambac) CVAs on interest rate derivatives is mitigated by the existence of collateral posting agreements under which adequate collateral has been posted. Certain of these 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 determination of their fair value. Ambac holds warrants to purchase equity shares of development stage companies. These warrants have a fair value of $1 and $1 as of June 30, 2024 and December 31, 2023, respectively. Fair value was determined using a standard warrant valuation model with internally developed input assumptions. Financial Guarantees: Fair value of net financial guarantees written represents our estimate of the cost to Ambac to completely transfer its insurance obligation to another market participant of comparable credit worthiness. In theory, this amount should be the same amount that another market participant of comparable credit worthiness would hypothetically charge in the marketplace, on a present value basis, to provide the same protection as of the balance sheet date. This fair value estimate of financial guarantees is presented on a net basis and includes direct and assumed contracts written, net of ceded reinsurance contracts. Long-term Debt: Long-term debt includes AAC surplus notes and the Ambac UK debt issued in connection with a policy commutation. The fair values of surplus notes is based on prices received from third-party sources and are classified as Level 2. The fair value of Ambac UK debt estimated based upon internal valuation models and is classified as Level 3. Other Financial Assets and Liabilities: Included in Other assets are loans, the fair values of which are estimated based upon internal valuation models and are classified as Level 3. Variable Interest Entity Assets and Liabilities: The financial assets and liabilities of Legacy Financial Guarantee Insurance VIEs ("FG VIEs") consolidated under the Consolidation Topic of the ASC consist primarily of fixed maturity securities and loans held by the VIEs, derivative instruments and notes issued by the VIEs which are reported as long-term debt. As described in Note 8. Variable Interest Entities , these FG VIEs are securitization entities which have liabilities and/or assets guaranteed by AAC or Ambac UK. The fair values of FG VIE long-term debt are based on price quotes received from independent market sources when available. Such quotes are considered Level 2 and generally consider a variety of factors, including recent trades of the same and similar securities. For those instruments where quotes were not available or cannot be reasonably corroborated, fair values are based on internal valuation models. Comparable to the sensitivities of investments in fixed maturity securities described above, longer (shorter) expected maturities or higher (lower) yields used in the valuation model will, in isolation, result in decreases (increases) in fair value liability measurement for FG VIE long-term debt. FG VIE derivative asset and liability fair values are determined using vendor-developed valuation models, which incorporated observable market data related to specific derivative contractual terms including interest rates, foreign exchange rates and yield curves. The fair value of FG VIE fixed maturity securities and loan assets are generally based on Level 2 market price quotes received from independent market sources when available. When FG VIE asset fair values are not readily available from market quotes, values are estimated internally. Internal valuations of FG VIE’s fixed maturity securities or loan assets are derived from the fair values of the notes issued by the respective VIE and the VIE’s derivatives, determined as described above, adjusted for the fair values of Ambac’s financial guarantees associated with the VIE. The fair value of financial guarantees consist of: (i) estimated future premium cash flows discounted at a rate consistent with that implicit in the fair value of the VIE’s liabilities and (ii) estimates of future claim payments discounted at a rate that includes Ambac’s own credit risk. Estimated future premium payments to be paid by the VIEs were discounted at a weighted average rate of 6.6% and 6.3% at June 30, 2024 and December 31, 2023, respectively. At June 30, 2024, the range of these discount rates was between 5.8% and 8.2%. At December 31, 2023, the range of these discount rates were between 5.3% and 7.8%. Additional Fair Value Information for Financial Assets and Liabilities Accounted for at Fair Value: The following tables present the changes in the Level 3 fair value category for the periods presented in 2024 and 2023. 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 Investments Derivatives Investments Loans Total Three Months Ended June 30, 2024: Balance, beginning of period $ 87 $ 21 $ 2,070 $ 1,604 $ 3,782 Total gains/(losses) realized and unrealized: Included in earnings 7 (3) (51) 29 (19) Included in other comprehensive income 9 — 3 3 15 Settlements (26) — (12) (68) (106) Balance, end of period $ 77 $ 18 $ 2,010 $ 1,567 $ 3,672 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 $ 7 $ (3) $ (51) $ 29 $ (19) The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 9 $ — $ 3 $ 3 $ 15 Three Months Ended June 30, 2023: Balance, beginning of period $ 81 $ 31 $ 2,003 $ 1,856 $ 3,972 Total gains/(losses) realized and unrealized: Included in earnings — (5) (53) (66) (124) Included in other comprehensive income — — 14 50 64 Settlements — — (12) (69) (81) Balance, end of period $ 81 $ 25 $ 1,952 $ 1,772 $ 3,831 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 $ — $ (5) $ (53) $ (66) $ (124) The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ — $ — $ 14 $ 50 $ 64 Level 3 - Financial Assets and Liabilities Accounted for at Fair Value VIE Assets Investments Derivatives Investments Loans Total Six Months Ended June 30, 2024: Balance, beginning of period $ 87 $ 26 $ 2,072 $ 1,663 $ 3,848 Additions of VIEs consolidated — Total gains/(losses) realized and unrealized: Included in earnings 7 (8) (32) 49 16 Included in other comprehensive income 9 — (18) (14) (23) Purchases — — — — — Settlements (27) — (12) (132) (170) Balance, end of period $ 77 $ 18 $ 2,010 $ 1,567 $ 3,672 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 $ 7 $ (8) $ (32) $ 49 $ 16 The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 9 $ — $ (18) $ (14) $ (23) Six Months Ended June 30, 2023: Balance, beginning of period $ 79 $ 26 $ 1,828 $ 1,829 $ 3,762 Additions of VIEs consolidated — — — — — Total gains/(losses) realized and unrealized: Included in earnings 1 — 80 (7) 73 Included in other comprehensive income 3 — 57 92 152 Purchases — — — — — Settlements (1) — (12) (141) (155) Balance, end of period $ 81 $ 25 $ 1,952 $ 1,772 $ 3,831 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 $ — $ 80 $ (7) $ 73 The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 3 $ — $ 57 $ 92 152 Invested assets and VIE long-term debt are transferred into Level 3 when internal valuation models that include significant unobservable inputs are used to estimate fair value. All such securities that have internally modeled fair values have been classified as Level 3. Derivative instruments are transferred into Level 3 when the use of unobservable inputs becomes significant to the overall valuation. There were no transfers of financial instruments into or out of Level 3 in the periods disclosed. Gains and losses (realized and unrealized) relating to Level 3 assets and liabilities included in earnings for the affected periods are reported as follows: Three Months Ended June 30, 2024 Three Months Ended June 30, 2023 Net Net Gains Income (Loss) Other Net Net Gains Income (Loss) Other Total gains (losses) included in earnings for the period $ 7 $ (3) $ (22) $ — $ — $ (5) $ (119) $ — Changes in unrealized gains (losses) relating to financial instruments still held at the reporting date 9 (3) (22) — — (5) (119) — Six Months Ended June 30, 2024 Six Months Ended June 30, 2023 Net Net Gains Income (Loss) Other Net Net Gains Income (Loss) Other Total gains or losses included in earnings for the period $ 7 $ (8) $ 17 $ — $ 1 $ — $ 72 $ — Changes in unrealized gains or losses included in earnings relating to the assets and liabilities still held at the reporting date 9 (8) 17 — — — 72 —

Derivative Instruments

Derivative Instruments	6 Months Ended
	Jun. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	6. 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 June 30, 2024 and December 31, 2023: June 30, 2024 December 31, 2023 Gross Gross Net Amounts Gross Amount Net Gross Gross Net Amounts Gross Amount Net Other assets: Interest rate swaps $ 18 $ — $ 18 $ — $ 18 $ 25 $ — $ 25 $ — $ 25 Warrants 1 — 1 — 1 1 — 1 — 1 Total non-VIE derivative assets $ 18 $ — $ 18 $ — $ 18 $ 26 $ — $ 26 $ — $ 26 Other liabilities: Interest rate swaps $ 25 $ — $ 25 $ 25 $ — $ 35 $ — $ 35 $ 35 $ — FX forward — — — — — — — — — — Total non-VIE derivative liabilities $ 26 $ — $ 26 $ 25 $ — $ 35 $ — $ 35 $ 35 $ — Variable interest entities assets: Derivative and other assets: Interest rate swaps $ 174 $ — $ 174 $ 174 $ — $ 190 $ — $ 190 $ 190 $ — Currency swaps 34 — 34 34 — 36 — 36 36 — Total VIE derivative assets $ 208 $ — $ 208 $ 208 $ — $ 226 $ — $ 226 $ 226 $ — Variable Interest Entities Derivative Liabilities: Interest rate swaps $ 1,136 $ — $ 1,136 $ — $ 1,136 $ 1,197 $ — $ 1,197 $ — $ 1,197 Total VIE derivative liabilities $ 1,136 $ — $ 1,136 $ — $ 1,136 $ 1,197 $ — $ 1,197 $ — $ 1,197 Amounts representing 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 Unaudited Consolidated Balance Sheets. The amounts representing the right to reclaim cash collateral and posted margin, recorded in “Other assets” were $18 and $23 as of June 30, 2024 and December 31, 2023, respectively. Amounts representing an obligation to return cash collateral were $52 and $235 as of June 30, 2024 and December 31, 2023, respectively and are reported in "Variable interest entity liabilities: Other liabilities". The following tables summarize the location and amount of gains and losses of derivative contracts in the Unaudited Consolidated Statements of Total Comprehensive Income (Loss) for the three and six months ended June 30, 2024 and 2023: Location of Gain (Loss) Amount of Gain (Loss) Recognized in Consolidated Statement of Total Comprehensive Income (Loss) Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Non-VIE derivatives: Interest rate swaps Net gains (losses) on derivative contracts 1 1 2 (3) Warrants Net gains (losses) on derivative contracts — — — — FX Forward Net gains (losses) on derivative contracts — — — — Total Non-VIE derivatives $ — $ — 2 (3) Variable Interest Entities: Currency swaps Income (loss) on variable interest entities $ — $ (1) 2 (3) Interest rate swaps Income (loss) on variable interest entities 43 97 57 (2) Total Variable Interest Entities 44 96 59 (5) Total derivative contracts $ 44 $ 97 $ 61 $ (8) Interest Rate Derivatives: AFS provided interest rate derivatives to financial guarantee customers and used derivatives to provide a partial hedge against interest rate risk in AAC's insurance and investment portfolios. Additionally, AFS provided interest rate swaps to states, municipalities and their authorities, asset-backed issuers and other entities in connection with their financings. AFS's only remaining derivative positions include a limited number of legacy customer swaps and their associated hedges. As of June 30, 2024 and December 31, 2023, the notional amounts of AFS’s derivatives are as follows: Notional Type of Derivative June 30, December 31, Interest rate swaps—pay-fixed/receive-variable $ 140 $ 141 Interest rate swaps—receive-fixed/pay-variable 159 167 Other Derivatives: As of June 30, 2024 Ambac holds warrants to purchase equity shares of development stage companies and is party to a US dollar / British pound sterling foreign exchange forward contract to protect against currency fluctuations related to the purchase of Beat. 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 amounts for VIE derivatives outstanding as of June 30, 2024 and December 31, 2023, were as follows: Notional Type of VIE Derivative June 30, December 31, Interest rate swaps—receive-fixed/pay-variable $ 1,648 $ 1,662 Interest rate swaps—pay-fixed/receive-variable 820 864 Currency swaps 136 149 Contingent Features in Derivatives Related to Ambac Credit Risk Certain of Ambac's interest rate swaps remain with professional swap-dealer counterparties 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 AAC is no longer rated by an independent rating agency, counterparties have the right to terminate the swap positions. As of June 30, 2024 and December 31, 2023, the net liability fair value of derivative instruments with contingent features linked to Ambac’s own credit risk was $25 and $35, respectively, related to which Ambac had posted cash and securities as collateral with a fair value of $44 and $50, respectively. All such ratings-based contingent features have been triggered requiring maximum collateral levels to be posted by Ambac while preserving counterparties’ rights to terminate the contracts. Assuming all such contracts terminated at fair value on June 30, 2024, 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.

Intangible Assets

Intangible Assets	6 Months Ended
	Jun. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	The following table presents the Company's goodwill. June 30, December 31, Beginning balance $ 70 $ 61 Business acquisitions — 9 Impairments — — Ending balance $ 70 $ 70
Goodwill and Intangible Assets Disclosure	7. GOODWILL AND INTANGIBLE ASSETS The following table presents the Company's goodwill. June 30, December 31, Beginning balance $ 70 $ 61 Business acquisitions — 9 Impairments — — Ending balance $ 70 $ 70 Intangible assets and accumulated amortization are included in the Consolidated Balance Sheets, as shown below. June 30, December 31, Finite-lived Intangible Assets: Insurance intangible: Gross carrying value $ 1,256 $ 1,258 Accumulated amortization 1,030 1,013 Net insurance intangible asset 226 245 Other intangibles: Gross carrying value 57 57 Accumulated amortization 12 10 Net other intangible assets 45 47 Total finite-lived intangible assets 271 292 Indefinite-lived Intangible Assets: Insurance licenses 14 14 Total intangible assets $ 285 $ 307

Comprehensive Income

Comprehensive Income	6 Months Ended
	Jun. 30, 2024
Equity [Abstract]
Comprehensive Income	10. COMPREHENSIVE INCOME The following tables detail the changes in the balances of each component of accumulated other comprehensive income for the affected periods: Three Months Ended June 30, 2024: Three Months Ended June 30, 2023: Unrealized Gains (1) Amortization of Postretirement Benefit (1) Gain (Loss) on Foreign Currency (1) Credit Risk Changes of Fair Value Option Liabilities (1) (2) Total Unrealized Gains (1) Amortization of Postretirement Benefit (1) Gain (Loss) on Foreign Currency (1) Credit Risk Changes of Fair Value Option Liabilities (1) (2) Total Beginning Balance $ (27) $ 5 $ (152) $ (1) $ (175) $ (54) $ 6 $ (168) $ (1) $ (217) Other comprehensive income (loss) before reclassifications 8 — 1 — 9 (15) — 21 — 6 Amounts reclassified from accumulated other comprehensive income (loss) (4) (5) — — (9) 3 — — — 2 Net current period other comprehensive income (loss) 4 (5) 1 — — (13) — 21 — 8 Ending Balance $ (23) $ — $ (151) $ (1) $ (175) $ (67) $ 6 $ (147) $ (1) $ (209) Six Months Ended June 30, 2024 Six Months Ended June 30, 2023 Unrealized Gains (1) Amortization of Postretirement Benefit (1) Gain (Loss) on Foreign Currency (1) Credit Risk Changes of Fair Value Option Liabilities (1) (2) Total Unrealized Gains (1) Amortization of Postretirement Benefit (1) Gain (Loss) on Foreign Currency (1) Credit Risk Changes of Fair Value Option Liabilities (1) (2) Total Beginning Balance $ (20) $ 5 $ (144) $ (1) $ (160) $ (71) $ 3 $ (184) $ (1) $ (253) Other comprehensive income before reclassifications 1 — (7) — (5) (1) 3 37 — 39 Amounts reclassified from accumulated other comprehensive income (5) (5) — — (10) 6 (1) — — 5 Net current period other comprehensive income (3) (5) (7) — (15) 5 2 37 — 44 Ending Balance $ (23) $ — $ (151) $ (1) $ (175) $ (67) $ 6 $ (147) $ (1) $ (209) (1) All amounts are net of tax and noncontrolling interest. Amounts in parentheses indicate reductions to Accumulated Other Comprehensive Income. (2) Represents the changes in fair value attributable to instrument-specific credit risk of liabilities for which the fair value option is elected. The following table details the significant amounts reclassified from each component of accumulated other comprehensive income, shown in the above rollforward tables, for the affected periods: Details about Accumulated Amount Reclassified from Affected Line Item in the Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Unrealized Gains (Losses) on Available-for-Sale Securities $ (4) $ 3 $ (4) $ 8 Net realized investment gains (losses) — (1) — (2) Provision for income taxes $ (4) $ 3 $ (5) $ 6 Net of tax and noncontrolling interest Amortization of Postretirement Benefit Prior service cost $ — $ — $ — $ — Other income Actuarial (losses) — — — — Other income Curtailment gain (5) — (5) — Other income (5) — (5) (1) Total before tax — — — — Provision for income taxes $ (5) $ — $ (5) $ (1) Net of tax and noncontrolling interest Credit Risk Changes of Fair Value Option Liabilities $ — $ (1) $ — $ — Credit risk changes of fair value option liabilities — — — — Provision for income taxes $ — $ — $ — $ — Net of tax and noncontrolling interest Total reclassifications for the period $ (9) $ 2 $ (9) $ 5 Net of tax and noncontrolling interest

Net Income Per Share

Net Income Per Share	6 Months Ended
	Jun. 30, 2024
Earnings Per Share [Abstract]
Net Income Per Share	11. NET INCOME PER SHARE As of June 30, 2024, 45,224,972 shares of AFG's common stock (par value $0.01) were issued and outstanding. Common shares outstanding increased by 29,602 during the six months ended June 30, 2024, primarily due to settlements of employee restricted and performance stock units. Earnings Per Share Calculation The numerator of the basic and diluted earnings per share computation represents net income (loss) attributable to common stockholders adjusted by the retained earnings impact of the noncontrolling adjustment to redemption value under ASC 480. The redemption value adjustment is further described in the Redeemable Noncontrolling Interest section of Note 1. Business and Basis of Presentation. The following table provides a reconciliation of net income attributable to common stockholders to the numerator in the basic and diluted earnings per share calculation, together with the resulting earnings per share amounts: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Net income (loss) attributable to common stockholders $ (1) $ (13) $ 19 (47) Adjustment to redemption value (ASC 480) — — — — Numerator of basic and diluted EPS $ (1) $ (13) $ 19 (47) Per Share: Basic $ (0.02) $ (0.29) $ 0.42 $ (1.02) Diluted $ (0.02) $ (0.29) $ 0.41 $ (1.02) The denominator of the basic earnings per share computation represents the weighted average common shares outstanding plus vested performance and restricted stock units (together, "Basic Weighted Average Shares Outstanding"). The denominator of diluted earnings per share adjusts the Basic Weighted Average Shares Outstanding for all potential dilutive common shares outstanding during the period. All potential dilutive common shares outstanding consider common stock deliverable pursuant to warrants, unvested restricted stock units and performance stock units granted under existing compensation plans. The following table provides a reconciliation of the weighted average shares denominator used for basic net income per share to the denominator used for diluted net income per share: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Basic weighted average shares outstanding denominator 46,209,250 45,757,234 46,019,145 45,661,288 Effect of potential dilutive shares : Restricted stock units — — 158,132 — Performance stock units (1) — — 391,585 — Diluted weighted average shares outstanding denominator 46,209,250 45,757,234 46,568,862 45,661,288 Anti-dilutive shares excluded from the above reconciliation: Warrants — — — — Restricted stock units 471,541 556,602 44,362 555,981 Performance stock units (1) 464,272 667,365 — 667,365 (1) Performance stock units are reflected based on the performance metrics through the balance sheet date. Vesting of these units is contingent upon meeting certain performance metrics. Although a portion of these performance metrics have been achieved as of the respective period end, it is possible that awards may no longer meet the metric at the end of the performance period.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2024
Income Tax Disclosure [Abstract]
Income Taxes	12. INCOME TAXES AFG files a consolidated Federal income tax return with its subsidiaries. AFG 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 2015 New York City 2018 United Kingdom 2020 Italy 2019 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 U.S. federal, state and/or local taxable income to recover its deferred tax operating assets and therefore maintains a full valuation allowance. Consolidated Pretax Income (Loss) U.S. and foreign components of pre-tax income (loss) were as follows: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 U.S. $ (11) $ (18) $ (1) $ (66) Foreign 13 7 28 26 Total $ 2 $ (11) $ 27 $ (40) 1 Provision (Benefit) for Income Taxes The components of the provision for income taxes were as follows: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Current taxes U. S. federal $ — $ 1 $ — $ 1 U.S. state and local — — — — Foreign 2 — 7 2 Total Current taxes 2 2 7 4 Deferred taxes Foreign — — 1 2 Total Deferred taxes — — 1 2 Provision for income taxes $ 2 $ 2 $ 7 $ 6

Compensation Related Costs, Pos

Compensation Related Costs, Postemployment Benefits	6 Months Ended
	Jun. 30, 2024
Postemployment Benefits [Abstract]
Compensation and Employee Benefit Plans	13

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	14. COMMITMENTS AND CONTINGENCIES The following commitments and contingencies provide an update of those discussed in Note 19: 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, 2023, and should be read in conjunction with the complete descriptions provided in the aforementioned Form 10-K. Litigation Against Ambac - Pending Cases Monterey Bay Military Housing, LLC, et al. v. Ambac Assurance Corporation, et al. (United States District Court, Southern District of New York, Case No. 1:19-cv-09193-PGG, transferred on October 4, 2019 from the United States District Court, Northern District of California, San Jose Division, Case No. 17-cv-04992-BLF, filed August 28, 2017). On April 6, 2022, certain co-defendants filed a motion to sever the plaintiffs’ claims and to dismiss all claims except for claims asserted by the Monterey Bay plaintiffs. On January 26, 2024, the court granted the parties leave to file motions for summary judgment; opening briefs were due March 22, 2024, while oppositions are due May 31, 2024 and replies on July 12, 2024. On February 29, 2024, the court denied co-defendants’ motion to sever plaintiffs’ claims. On March 22, 2024, defendants served opening motions for summary judgment against plaintiffs’ claims in their entirety on multiple grounds, and plaintiffs served cross-motions for summary judgment on defendants’ unclean hands defenses. The parties’ summary judgment motions were fully briefed as of July 12, 2024 and are currently awaiting a decision from the Court. In re National Collegiate Student Loan Trusts Litigation (Delaware Court of Chancery, Consolidated C.A. No. 12111, filed November 1, 2019). The Vice Chancellor entered a series of stays to facilitate good-faith settlement discussions, the most recent of which was entered on May 2, 2023, and stayed the matter through May 5, 2023. On April 25, 2024, the Administrator filed a status report stating that certain parties continue to negotiate a resolution to the various pending claims. Litigation Against Ambac - General AAC’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 and have commenced, or threatened to commence, litigation to resolve these differences. It is not possible to predict whether additional disputes will arise, nor the outcomes of any potential litigation. It is possible that there could be unfavorable outcomes in this or other disputes or proceedings and that our interpretations may prove to be incorrect, which could lead to changes to our estimate of loss reserves. The Company periodically receives various regulatory inquiries and requests for information with respect to investigations and inquiries that such regulators are conducting. The Company has complied with all such inquiries and requests for information. The Company is involved from time to time in various routine legal proceedings, including proceedings related to litigation with present or former employees. Although such litigation routine and incidental to the conduct of its business, such litigation can potentially result in large monetary awards when a civil jury is allowed to determine compensatory and/or punitive damages. Everspan may be subject to disputes with policyholders or other third parties regarding the scope and extent of coverage offered under Everspan's policies, including disputes relating to Everspan’s course of conduct in the handling of claims and settling or failing to settle claims (which can lead to bad faith and other forms of extra-contractual liability); be required to defend claimants in suits against its policyholders for covered liability claims; or enter into commercial disputes with its reinsurers, MGA/Us or third party claims administrators regarding their respective contractual obligations and rights. Under some circumstances, the results of such disputes or suits may lead to liabilities beyond those which are anticipated or reserved, including liabilities in excess of applicable policy limits. From time to time, Ambac is subject to allegations concerning its corporate governance that may lead to litigation, including derivative litigation, and while the monetary impacts may not be material, the matters may distract management and the Board of Directors from their principal focus on Ambac's business, strategy and objectives. 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 the Company with losses that are probable and reasonably estimable are not material to the operating results or financial position of the Company. For the litigation matters the Company is defending that do not meet the “probable and reasonably estimable” accrual threshold and where no loss estimates have been provided, management is unable to make a meaningful estimate of the amount or range of loss that could result from unfavorable outcomes. 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 or Joined by Ambac CFPB v. Nat’l Collegiate Master Student Loan Trust (United States District Court, District of Delaware, Case No. 1:17-cv-01323, filed September 18, 2017). The CFPB filed an amended complaint on April 30, 2021. On May 21, 2021, the Trusts and several intervenors, including AAC, moved to dismiss the CFPB’s amended complaint for failure to state a claim. On December 13, 2021, the court denied the Trusts' and intervenors' motions to dismiss the amended complaint. On December 23, 2021, the Trusts and several intervenors, including AAC, filed a motion seeking (i) an order certifying for interlocutory appeal the court’s December 13, 2021 order denying the motion to dismiss the amended complaint, and (ii) a stay of the action pending resolution of any appeal. On January 26, 2022, the Trusts and several intervenors, including AAC, answered the CFPB’s

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Pay vs Performance Disclosure
Net income attributable to common shareholders	$ (1)	$ (13)	$ 19	$ (47)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false	false
Rule 10b5-1 Arrangement Terminated		false

Business and Basis of Present_2

Business and Basis of Presentation Financial Services, Insurance (Policies)	6 Months Ended
	Mar. 31, 2025	Jun. 30, 2024
Insurance [Abstract]
Consolidation, Policy		Consolidation The consolidated financial statements include the accounts of AFG and all other entities in which AFG (directly or through its subsidiaries) has a controlling financial interest, including variable interest entities (“VIEs”) for which AFG or an AFG subsidiary is deemed the primary beneficiary in accordance with the Consolidation Topic of the Accounting Standards Codification ("ASC"). All significant intercompany balances have been eliminated. See Note 8. Variable Interest Entities
New Accounting Pronouncements, Policy [Policy Text Block]		Adopted Accounting Standards There have been no new accounting standards adopted during 2024. Future Application of Accounting Standards and Required Disclosures Segment Reporting In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280) - Improvement to Reportable Segment Disclosures . The ASU requires disclosure of the following: • Significant segment expenses regularly provided to the chief operating decision maker (CODM) and included within the reported measure(s) of a segment’s profit or loss. • The amount and composition of "other segment items." This amount reconciles segment revenue, less significant expenses, to the reported measure(s) of a segment’s profit or loss. • The CODM's title and position. • How the CODM uses the reported measure(s) of a segment’s profit or loss to assess segment performance and decide how to allocate resources. • All segment profit or loss and assets disclosures currently required annually by Topic 280, as well as those introduced by the ASU, to also be disclosed in interim periods. The ASU also permits a public entity to report multiple measures of a segment’s profit or loss as long as: i) all the reported measures of a segment’s profit or loss are used by the CODM for purposes of assessing performance and allocating resources and ii) the measure closest to GAAP is also provided. The ASU is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. Ambac will adopt this ASU for the annual reporting period ending December 31, 2024 and we are evaluating its impact on Ambac's financial statements. Income Taxes In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures . The enhancements in the ASU include the following: • Within the rate reconciliation table, disclosure of additional categories of information about federal, state and foreign income taxes and providing more details about the reconciling items in some categories if the items meet a quantitative threshold. • Annual disclosure of income taxes paid (net of refunds received) disaggregated by federal (national), state and foreign taxes and disaggregation of the information by jurisdiction based on a quantitative threshold. • Other disclosures include: i) income (or loss) from continuing operations before income tax expense (or benefit) disaggregated between domestic and foreign and ii) income tax expense (or benefit) from continuing operations disaggregated by federal (national), state, and foreign. The ASU is effective for annual periods beginning after December 15, 2024, with early adoption permitted. Ambac will adopt this ASU on January 1, 2025 and we are evaluating its impact on Ambac's financial statements.
Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block]	1. BUSINESS AND BASIS OF PRESENTATION Business The following description provides an update of Note 1. Background and Business Description and Note 2. Basis of Presentation and Significant Accounting Policies in the Notes to the Consolidated Financial Statements included in Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023, and should be read in conjunction with the complete descriptions provided in the Form 10-K. Capitalized terms used, but not defined herein, and in the other footnotes to the Consolidated Financial Statements included in this Quarterly Report on Form 10-Q shall have the meanings ascribed thereto in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. Ambac Financial Group, Inc. (“AFG”), headquartered in New York City, is a specialty insurance holding company incorporated in the state of Delaware on April 29, 1991. References to “Ambac,” the “Company,” “we,” “our,” and “us” are to AFG and its subsidiaries, as the context requires. Ambac's principal businesses include: • Specialty Property & Casualty Insurance — Ambac's Specialty Property & Casualty Insurance program business. Currently includes six carriers (collectively, “Everspan”). Everspan carriers have an A.M. Best rating of 'A-' (Excellent) that was affirmed on June 13, 2024. • Insurance Distribution — Ambac's specialty property and casualty ("P&C") insurance distribution business, which could include Managing General Agents and Underwriters (collectively "MGAs"), insurance brokers, and other distribution businesses. At June 30, 2024 Ambac's insurance distribution platform includes five businesses that operate in the following lines of business: accident and health, specialty commercial automobile insurance for specific "for-hire" auto clauses, marine and international risk and professional liability. • Legacy Financial Guarantee Insurance — Ambac's legacy financial guarantee business includes the activities of Ambac Assurance Corporation ("AAC") and its wholly owned subsidiaries, including Ambac Assurance UK Limited (“Ambac UK”) and Ambac Financial Services LLC ("AFS"). Both AAC and Ambac UK (the "Legacy Financial Guarantee Companies") have financial guarantee insurance portfolios that have been in runoff since 2008. AFS provided interest rate derivatives to financial guarantee customers and used derivatives to hedge interest rate risk in AAC's insurance and investment portfolios. AFS' remaining derivative positions include a limited number of legacy customer swaps and their associated hedges. The Company reports these three business operations as segments; see Note 2. Segment Information for further information. Sale of Ambac Assurance Corporation ("AAC") On June 4, 2024, AFG entered into a stock purchase agreement (the "Purchase Agreement") with American Acorn Corporation (the “Buyer”), a Delaware corporation owned by funds managed by Oaktree Capital Management, L.P., pursuant to which and subject to the conditions set forth therein, AFG will sell all of the issued and outstanding shares of common stock of AAC, a wholly-owned subsidiary of AFG, to Buyer for aggregate consideration of $420 in cash (the "Sale"). The terms of the Sale as contemplated by the Purchase Agreement provide that, at the closing of the Sale (the “Closing”), Buyer will acquire complete ownership of the common stock of AAC and all of its wholly owned subsidiaries, including Ambac UK. The Purchase Agreement provides that AFG will seek the affirmative vote in favor of the Sale by the holders of a majority of the issued and outstanding shares of AFG common stock entitled to vote thereon (the “Stockholder Approval”). On August 2, 2024, AFG filed a preliminary proxy statement with the SEC, which proxy statement includes the recommendation of the board of directors of AFG that the Sale be approved by shareholders of AFG. The Purchase Agreement contains certain customary termination rights for each of AFG and Buyer, including (i) by mutual written agreement, (ii) if the Sale has not been consummated on or before April 4, 2025 (the “End Date”), subject to certain extensions for 90 days, (iii) the other party is in breach of the Purchase Agreement in a manner that would result in a failure of an applicable closing condition and such breach cannot be cured or, if curable, has not been cured within 60 days after written notice to the other party of such breach, (iv) the Stockholder Approval is not received, or (v) if any applicable law makes the consummation of the Closing illegal or otherwise prohibited or any judgment, order or decree of any governmental authority enjoins Buyer and AFG from consummating the Closing. In addition, Buyer may terminate the Purchase Agreement if AFG changes its recommendation to AFG's stockholders regarding the Sale. AFG would pay Buyer an amount equal to $22 (the “Termination Fee”) if all of the following occur: (i) the Purchase Agreement is terminated as a result of (a) not closing the Sale and other transactions contemplated by the Purchase Agreement by the End Date, subject to certain conditional extension for 90 days, (b) failure to obtain the Stockholder Approval or (c) an AFG breach of representations or covenants that would cause certain closing conditions not to be satisfied, (ii) AFG has received an alternative acquisition proposal prior to a valid termination of the Purchase Agreement, and (iii) within 12 months after termination of the Purchase Agreement, AFG enters into a definitive agreement for an alternative acquisition. AFG would also pay Buyer the Termination Fee if the Purchase Agreement is terminated for (x) AFG breach of certain covenants that would cause closing conditions not to be satisfied, (y) failure to obtain the Stockholder Approval at a time when Buyer could have terminated the Purchase Agreement for an AFG breach of certain covenants that would cause closing conditions not to be satisfied, or (z) AFG changing its recommendation to the Company’s stockholders regarding the sale. In addition to the Termination Fee, AFG would pay Buyer up to $6 as a reimbursement of Buyer’s reasonably documented out-of-pocket fees and expenses incurred in connection with the Sale and other transactions contemplated by the Purchase Agreement if (i) the Purchase Agreement is terminated as a result of not closing the Sale and other transactions by the End Date and the Termination Fee is also payable, (ii) there is a failure to obtain the Stockholder Approval when the Buyer could have terminated the Purchase Agreement because there is an AFG breach of representations or covenants related to regulatory efforts, non-solicitation or the AFG stockholders meeting that would cause certain closing conditions not to be satisfied, (iii) the Purchase Agreement is terminated as a result of AFG changing its recommendation to the AFG stockholders regarding the Sale, or (iv) there is an AFG breach of representations or covenants that would cause certain closing conditions not to be satisfied. The Closing is subject to customary closing conditions, including the receipt of specified regulatory approvals and the Stockholder Approval. In connection with and pursuant to the Purchase Agreement, AFG has agreed to issue to Buyer a warrant exercisable for a number of shares of common stock, par value $0.01, of AFG representing 9.9% of the fully diluted shares of AFG’s common stock as of March 31, 2024, pro forma for the issuance of the Warrant. The Warrant will have an exercise price per share of $18.50 with a 6.5 year term from the date of issuance and will be immediately exercisable. Payment of the exercise price may be settled, at AFG’s option, by way of a cash exercise or by net share settlement. While management and the Board have approved the Sale, the final commitment to sell AAC is subject to approval by our shareholders and regulators in both the US and UK. The Sale will have a major effect on AFG's operations and financial results and therefore at the date we meet the held-for-sale reporting requirements, we will report the pending sale as a discontinued operation. At June 30, 2024, the carrying value of AFG's investment in AAC is approximately $939. Once the shareholders vote is obtained and regulatory approval is probable, a loss on the transaction will be reflected in the Statement of Comprehensive Income equal to the difference between the sales proceeds (net of the value of the Warrants to be issued) and AAC's carrying value. Additionally, net income will be adversely impacted by a reclassification from Accumulated Other Comprehensive Income relating to unrealized losses on available-for-sale investment securities, foreign currency translation losses and credit risk changes of fair value option liabilities, which at June 30, 2024 amounted to $168. The Sale is expected to close in the fourth quarter of 2024 or the first quarter of 2025. Acquisition of Beat Capital Partners Limited ("Beat") On June 4, 2024, the Company, entered into a share purchase agreement (the “Beat Purchase Agreement”), by and among the Company, Cirrata V LLC, a Delaware limited liability company and an indirect wholly owned subsidiary of AFG (the “Purchaser”), certain sellers set forth therein (the “Sellers”) and Beat, pursuant to which, effective July 31, 2024, the Purchaser purchased from the Sellers approximately 60% of the entire issued share capital of Beat for total consideration, as of the closing date, of approximately $278, of which approximately $249 was paid in cash and the remainder of which was satisfied through the issuance of 2,216,023 shares of AFG common stock to certain Sellers (the "Beat Transaction"). Beat’s management team and Bain Capital Credit LP (“Bain” and, together with certain members of Beat’s management team, the “Rollover Shareholders”) each retained approximately 20% of Beat’s issued share capital immediately after closing. AFG guaranteed the Purchaser’s performance under the Beat Purchase Agreement and the Shareholders’ Agreement (as defined below). AFG issued the common stock free and clear of any liens or restrictions (other than those arising under state and federal securities laws of the United States) and bearing a restrictive legend. The common stock has not been registered under the Securities Act in reliance upon an exemption from registration pursuant to Section 4(a)(2) of the Securities Act. AFG funded the cash portion of the consideration with a combination of available cash, approximately $65 of funding from AAC, and $150 of new indebtedness (the "Credit Facility") that was issued in the third quarter of 2024. Funding received from AAC and the Credit Facility are required to be repaid upon closing of the sale of AAC. To reduce its exposure to appreciation of the British Pound Sterling ("GBP") relative to the U.S. Dollar ("USD"), AFG entered into a foreign exchange futures contract under which it agreed to purchase an amount of GBP sufficient to cover the cash portion of the purchase price of Beat along with estimated GBP denominated expenses at an exchange rate of 1.2662 per USD. At the closing of the Beat Transaction, AFG entered into a Shareholders’ Agreement by and among AFG, the Purchaser, the Rollover Shareholders and Beat (the “Shareholders’ Agreement”). The Shareholders’ Agreement provides for, among other things, the granting of (i) put options to each Rollover Shareholder to require the Purchaser to purchase from such Rollover Shareholder, the Relevant Shares (as defined in the Shareholders’ Agreement), and (ii) call options to the Purchaser to purchase from each Rollover Shareholder, the Relevant Shares. Basis of Presentation The Company has disclosed its 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, 2023. The following significant accounting policies provide an update to those included in the Company’s Annual Report on Form 10-K. 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 consolidated 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, 2023. 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 necessary for the fair presentation of the Company’s consolidated financial position and results of operations. The results of operations for the three and six months ended June 30, 2024, may not be indicative of the results that may be expected for the year ending December 31, 2024. The December 31, 2023, 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. Consolidation The consolidated financial statements include the accounts of AFG and all other entities in which AFG (directly or through its subsidiaries) has a controlling financial interest, including variable interest entities (“VIEs”) for which AFG or an AFG subsidiary is deemed the primary beneficiary in accordance with the Consolidation Topic of the Accounting Standards Codification ("ASC"). All significant intercompany balances have been eliminated. See Note 8. Variable Interest Entities , for a detailed discussion of Ambac’s involvement in VIEs, Ambac’s methodology for determining whether Ambac is required to consolidate a VIE and the effects of VIEs being consolidated and deconsolidated. Foreign Currency The impact of non-functional currency transactions and the remeasurement of non-functional currency assets and liabilities into the respective subsidiaries' functional currency (collectively "foreign currency transactions gains/(losses)") are $(1) and $(3) for the six months ended June 30, 2024 and 2023, respectively. Foreign currency transactions gains/(losses) are primarily the result of remeasuring Ambac UK's assets and liabilities denominated in currencies (primarily the U.S. dollar and the Euro) other than its functional currency (the British Pound Sterling). Redeemable Noncontrolling Interest The Riverton, All Trans, Capacity Marine and Xchange acquisitions resulted in a majority ownership of the acquired entities by Ambac. Under the terms of all the acquisition agreements, Ambac has call options to purchase the remaining interests from the minority owners (i.e., noncontrolling interests) and the minority owners have put options to sell their interests to Ambac. Because the exercise of the put options are outside the control of Ambac, in accordance with the Distinguishing Liabilities from Equity Topic of the ASC, Ambac reports redeemable noncontrolling interests in the mezzanine section of its consolidated balance sheet. The redeemable noncontrolling interest is remeasured each period as the greater of: i. the carrying value under ASC 810, which attributes a portion of consolidated net income (loss) to the redeemable noncontrolling interest, and ii. the redemption value of the put option under ASC 480 as if it were exercisable at the end of the reporting period. Any increase (decrease) in the carrying amount of the redeemable noncontrolling interest as a result of adjusting to the redemption value of the put option is recorded as an offset to retained earnings. The impact of such differences on earnings per share are presented in Note 11. Net Income Per Share . Following is a rollforward of redeemable noncontrolling interest. Six Months Ended June 30, 2024 2023 Beginning balance $ 17 $ 20 Fair value of redeemable noncontrolling interest at acquisition date — — Net income attributable to redeemable noncontrolling interest (ASC 810) 1 1 Distributions (1) (1) Adjustment to redemption value (ASC 480) — — Ending balance $ 17 $ 20 Supplemental Disclosure of Cash Flow Information Six Months Ended June 30, 2024 2023 Cash paid during the period for: Income taxes $ 7 $ 6 Interest on long-term debt — 50 Non-cash investing and financing activities: Securities acquired (transferred) in transactions related to Puerto Rico restructurings — (1) Securities acquired (transferred) in connection with financial guarantee commutations (65) — June 30, 2024 2023 Reconciliation of cash, cash equivalents, and restricted cash reported within the Cash and cash equivalents $ 24 $ 33 Restricted cash 11 10 Variable Interest Entity restricted cash 62 266 Total cash, cash equivalents, and restricted cash shown on the Consolidated Statements of Cash Flows $ 97 $ 309 Restricted cash is cash that we do not have the right to use for general purposes and includes fiduciary cash held by Ambac's insurance distribution subsidiaries, consolidated variable interest entity cash to support the obligations of the consolidated VIEs and cash received as collateral under their derivatives agreements. Reclassifications and Rounding Reclassifications may have been made to prior years' amounts to conform to the current year's presentation. Certain amounts and tables in the consolidated financial statements and associated notes may not add due to rounding. Adopted Accounting Standards There have been no new accounting standards adopted during 2024. Future Application of Accounting Standards and Required Disclosures Segment Reporting In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280) - Improvement to Reportable Segment Disclosures . The ASU requires disclosure of the following: • Significant segment expenses regularly provided to the chief operating decision maker (CODM) and included within the reported measure(s) of a segment’s profit or loss. • The amount and composition of "other segment items." This amount reconciles segment revenue, less significant expenses, to the reported measure(s) of a segment’s profit or loss. • The CODM's title and position. • How the CODM uses the reported measure(s) of a segment’s profit or loss to assess segment performance and decide how to allocate resources. • All segment profit or loss and assets disclosures currently required annually by Topic 280, as well as those introduced by the ASU, to also be disclosed in interim periods. The ASU also permits a public entity to report multiple measures of a segment’s profit or loss as long as: i) all the reported measures of a segment’s profit or loss are used by the CODM for purposes of assessing performance and allocating resources and ii) the measure closest to GAAP is also provided. The ASU is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. Ambac will adopt this ASU for the annual reporting period ending December 31, 2024 and we are evaluating its impact on Ambac's financial statements. Income Taxes In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures . The enhancements in the ASU include the following: • Within the rate reconciliation table, disclosure of additional categories of information about federal, state and foreign income taxes and providing more details about the reconciling items in some categories if the items meet a quantitative threshold. • Annual disclosure of income taxes paid (net of refunds received) disaggregated by federal (national), state and foreign taxes and disaggregation of the information by jurisdiction based on a quantitative threshold. • Other disclosures include: i) income (or loss) from continuing operations before income tax expense (or benefit) disaggregated between domestic and foreign and ii) income tax expense (or benefit) from continuing operations disaggregated by federal (national), state, and foreign. The ASU is effective for annual periods beginning after December 15, 2024, with early adoption permitted. Ambac will adopt this ASU on January 1, 2025 and we are evaluating its impact on Ambac's financial statements.
Foreign Currency Transactions and Translations Policy [Policy Text Block]		Foreign Currency The impact of non-functional currency transactions and the remeasurement of non-functional currency assets and liabilities into the respective subsidiaries' functional currency (collectively "foreign currency transactions gains/(losses)") are $(1) and $(3) for the six months ended June 30, 2024 and 2023, respectively. Foreign currency transactions gains/(losses) are primarily the

Segment Reporting (Policies)

Segment Reporting (Policies)	6 Months Ended
	Jun. 30, 2024
Segment Reporting [Abstract]
Segment Reporting, Policy	The Company reports its results of operations in three segments: Legacy Financial Guarantee Insurance, Specialty Property and Casualty Insurance and Insurance Distribution, separate from Corporate and Other, which is consistent with the manner in which the Company's chief operating decision maker ("CODM") reviews the business to assess performance and allocate resources.

Segment Reporting (Tables)

Segment Reporting (Tables)	6 Months Ended
	Jun. 30, 2024
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The following tables summarize the components of the Company’s total revenues and expenses, pretax income (loss) and total assets by reportable business segment. Information provided below for “Corporate and Other” primarily relates to the operations of AFG, which will include investment income on its investment portfolio and costs to maintain the operations of AFG, including public company reporting, capital management and business development costs for the acquisition and development of new business initiatives. Three Months Ended June 30, 2024 Three Months Ended June 30, 2023 Legacy Financial Guarantee Insurance Specialty Property & Casualty Insurance Insurance Distribution Corporate & Other Consoli-dated (2) Legacy Financial Guarantee Insurance Specialty Property & Casualty Insurance Insurance Distribution Corporate & Other Consoli-dated (2) Revenues: Net premiums earned $ 6 $ 27 $ 33 $ 8 $ 8 $ 15 Commission income $ 13 13 $ 10 10 Program fees 3 3 2 2 Net investment income 32 1 — $ 2 36 32 1 — $ 2 35 Net investment gains (losses), including impairments (1) — 5 4 (3) — — (3) Net gains (losses) on derivative contracts 1 — — 1 — — Other (1) 16 — — — 15 2 — — — 3 Total revenues (2) 53 32 13 6 105 39 11 10 2 62 Expenses: Losses and loss adjustment expenses (benefit) (5) 23 18 2 6 7 Amortization of deferred acquisition costs, net — 5 5 — 1 1 Commission expenses 8 8 6 6 General and administrative expenses (3) 22 5 3 17 47 23 4 2 6 36 Depreciation expense (3) — — — — 1 — — — — — Intangible amortization 7 1 8 6 1 7 Interest expense 16 16 16 16 Total expenses (2) 40 33 12 17 103 47 11 9 6 73 Pretax income (loss) $ 13 $ (1) $ 1 $ (11) $ 2 $ (8) $ — $ 1 $ (4) $ (11) Total assets (2) $ 7,100 $ 713 $ 155 $ 216 $ 8,184 $ 7,376 $ 395 $ 137 $ 225 $ 8,132 Six Months Ended June 30, 2024 Six Months Ended June 30, 2023 Legacy Financial Guarantee Insurance Specialty Property & Casualty Insurance Insurance Distribution Corporate & Other Consoli-dated (2) Legacy Financial Guarantee Insurance Specialty Property & Casualty Insurance Insurance Distribution Corporate & Other Consoli-dated (2) Revenues: Net premiums earned $ 13 $ 53 $ 66 $ 14 $ 15 $ 29 Commission income $ 31 $ 31 $ 25 $ 25 Program fees $ 6 $ 6 $ 4 $ 4 Net investment income (loss) $ 70 $ 3 $ — $ 4 $ 78 $ 63 $ 2 $ 4 $ 69 Net investment gains (losses), including impairments $ — $ — $ 5 $ 4 $ (8) $ — $ — $ (8) Net gains (losses) on derivative contracts $ 2 $ — $ 2 $ (3) $ — $ (3) Other (1) $ 21 $ — $ — $ — $ 21 $ 4 $ — $ — $ — $ 4 Total revenues (2) $ 107 $ 61 $ 31 $ 8 $ 207 $ 71 $ 20 $ 25 $ 4 $ 120 Expenses: Losses and loss adjustment expenses $ (26) $ 42 $ 16 $ 15 $ 10 $ 25 Amortization of deferred acquisition costs, net $ — $ 10 $ 10 $ — $ 3 $ 3 Commission expenses $ 18 $ 18 $ 14 $ 14 General and administrative expenses (3) $ 44 $ 8 $ 6 $ 24 $ 82 $ 52 $ 8 $ 5 $ 7 $ 72 Depreciation expense (3) $ — $ — $ — $ 1 $ 1 $ 1 $ — $ — $ — $ 1 Intangible amortization $ 18 $ 2 $ 21 $ 11 $ 2 $ 13 Interest expense $ 32 $ 32 $ 32 $ 32 Total expenses (2) $ 69 $ 61 $ 26 $ 24 $ 180 $ 111 $ 21 $ 20 $ 8 $ 160 Pretax income (loss) $ 38 $ 1 $ 5 $ (16) $ 27 $ (40) $ (1) $ 4 $ (3) $ (40) (1) Other revenues include the following line item on the Consolidated Statements of Total Comprehensive Income: Income (loss) on variable interest entities and other income. (2) Inter-segment revenues and inter-segment pre-tax income (loss) amounts are insignificant and are not presented separately. (3) The Consolidated Statements of Comprehensive Income presents the sum of these items as General & Administrative Expenses.

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2024
Investments, Debt and Equity Securities [Abstract]
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 June 30, 2024, by contractual maturity, were as follows: Amortized Estimated Due in one year or less $ 439 $ 437 Due after one year through five years 543 521 Due after five years through ten years 304 279 Due after ten years 132 124 1,418 1,361 Residential mortgage-backed securities 240 253 Commercial mortgage-backed securities 46 46 Collateralized debt obligations 141 141 Other asset-backed securities 234 241 Total $ 2,078 $ 2,043
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, excluding VIE investments, which at June 30, 2024 and December 31, 2023, did not have an allowance for credit losses This information is aggregated by investment category and length of time that the individual securities have been in a continuous unrealized loss position, at June 30, 2024 and December 31, 2023: June 30, 2024 December 31, 2023 Less Than 12 Months 12 Months or More Total Less Than 12 Months 12 Months or More Total Fair Gross Fair Gross Fair Gross Fair Gross Fair Gross Fair Gross Fixed maturity securities: Municipal obligations $ 21 $ — $ 15 $ 1 $ 35 $ 2 $ 7 $ — $ 16 $ 1 $ 23 $ 1 Corporate obligations 125 3 493 43 618 46 75 2 509 43 584 44 Foreign obligations 25 — 55 7 80 7 8 — 56 6 64 6 U.S. government obligations 58 1 37 3 95 4 27 1 37 2 63 4 Residential mortgage-backed securities 16 — 113 13 129 13 6 — 98 14 104 14 Commercial mortgage-backed securities 17 — — — 17 — 3 — — — 3 — Collateralized debt obligations 18 — 3 — 22 — 1 — 93 1 95 1 Other asset-backed securities 45 1 72 4 117 5 57 1 35 1 92 1 326 5 787 71 1,113 77 184 4 844 68 1,028 71 Short-term 46 — — — 46 — 4 — — — 4 — 372 5 787 71 1,159 77 187 4 844 68 1,032 71 U. S. government obligations 25 1 — — 25 1 — — — — — — Total collateralized investments 25 1 — — 25 1 — — — — — — Total temporarily impaired securities $ 398 $ 7 $ 787 $ 71 $ 1,184 $ 78 $ 187 $ 4 $ 844 $ 68 $ 1,032 $ 71
Summary of Amounts Included in Net Realized (Losses) Gains and Other-Than-Temporary Impairments	The following table details amounts included in net investment gains (losses) and impairments included in earnings for the affected periods: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Gross realized gains on securities $ 7 $ — $ 7 $ 1 Gross realized losses on securities (1) (2) (1) (3) Foreign exchange gains (losses) (1) (2) — (4) Credit impairments (2) — (1) (1) Intent / requirement to sell impairments — — — — Net investment gains (losses), including impairments $ 4 $ (3) $ 4 $ (8)
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 and weighted-average underlying rating of insured securities in Ambac's investment portfolio at June 30, 2024 and December 31, 2023, respectively: June 30, 2024 December 31, 2023 Municipal obligations $ 8 $ 9 Mortgage-backed securities 244 240 Asset-backed securities 151 232 Total $ 403 482 Weighted average underlying rating B- B- (1) Ratings are based on the lower of Standard & Poor’s or Moody’s rating. If unavailable, Ambac’s internal rating is used.
Equity Method Investments [Table Text Block]	In addition to these investments, Ambac has unfunded commitments of $30 to private credit and private equity funds at June 30, 2024. Fair Value Class of Funds June 30, December 31, 2023 Redemption Frequency Redemption Notice Period Hedge funds (1) $ 117 $ 112 quarterly or semi-annually 90 days Private credit (2) 83 84 quarterly if permitted 180 days if permitted High yields and leveraged loans (3) (10) 137 85 daily 0 - 30 days Equity market investments (4) (10) 40 38 daily 0 days Investment grade floating rate income (5) 53 52 weekly 0 days Private equity (6) 79 70 quarterly if permitted 90 days if permitted Real estate properties (7) — 21 see footnote (7) see footnote (7) Convertible bonds (8)(10) 23 — daily 0 days Insurance-linked investments (9) — 1 see footnote (9) see footnote (9) Total equity investments in pooled funds $ 533 $ 463 (1) This class seeks to generate superior risk-adjusted returns through selective asset sourcing, active trading and hedging strategies across a range of asset types. (2) This class aims to obtain high long-term returns primarily through credit and preferred equity investments with low liquidity and defined term. (3) This class of funds includes investments in a range of instruments including high-yield bonds, leveraged loans, CLOs, ABS and floating rate notes to generate income and capital appreciation. (4) This class of funds aim to achieve long term growth through diversified exposure to global equity-markets. (5) This class of funds includes investments in high quality floating rate debt securities including ABS and corporate floating rate notes. (6) This class seeks to generate long-term capital appreciation through investments in private equity, equity-related and other instruments. (7) Investments consisted of UK property to generate income and capital growth. The fund in which Ambac was invested has terminated on May 30, 2024 and is in the process of distributing remaining capital. Amounts owed Ambac from the fund are included in Other assets on the Consolidated Balance Sheet as of June 30, 2024. (8) This class seeks to generate total returns from portfolios focused primarily on convertible securities. (9) This class seeks to generate returns from insurance markets through investments in catastrophe bonds, life insurance and other insurance linked investments. This investment was restricted in connection with the unwind of certain insurance linked exposures. Ambac's investment was fully redeemed by March 31, 2024. (10)
Summary of Net Investment Income	Net investment income (loss) was comprised of the following for the affected periods: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Fixed maturity securities $ 22 $ 19 $ 45 $ 35 Short-term investments 5 5 10 10 Investment expense (1) (1) (3) (3) Securities available-for-sale and short-term 26 22 52 43 Fixed maturity securities - trading 2 4 4 5 Other investments 8 9 21 22 Total net investment income (loss) $ 36 $ 35 $ 78 $ 69
Debt Securities, Available-for-Sale	The amortized cost and estimated fair value of available-for-sale investments, excluding VIE investments, at June 30, 2024 and December 31, 2023, were as follows: June 30, 2024: December 31, 2023: Amortized Allowance for Credit Losses (2) Gross Unrealized Estimated Amortized Allowance for Credit Losses Gross Unrealized Estimated Gains Losses Gains Losses Fixed maturity securities: Municipal obligations $ 71 $ — $ 1 $ 2 $ 71 $ 72 — $ 1 $ 1 $ 72 Corporate obligations 786 — 2 46 742 785 — 4 44 745 Foreign obligations 111 — — 7 105 105 — 1 6 100 U.S. government obligations 108 — — 4 105 85 — 1 4 82 Residential mortgage-backed securities 240 3 28 13 253 239 3 28 14 250 Commercial mortgage-backed securities 46 — — — 46 19 — — — 19 Collateralized debt obligations 141 — 1 — 141 139 — 1 1 139 Other asset-backed securities (1) 234 — 12 5 241 301 — 3 1 303 1,737 3 45 77 1,703 1,744 3 40 71 1,710 Short-term 314 — — — 314 426 — — — 426 2,051 3 45 77 2,017 2,170 3 40 71 2,135 Fixed maturity securities pledged as collateral: U.S. government obligations 27 — — 1 25 — — — — — Short-term — — — — — 27 — — — 27 27 — — 1 25 27 — — — 27 Total available-for-sale investments $ 2,078 $ 3 $ 45 $ 78 $ 2,043 $ 2,197 3 $ 40 $ 71 $ 2,162 (1) Consists primarily of military housing and student loan securities. (2) For the three and six months ended June 30, 2024, the allowance for credit losses changed by $0 on residential mortgage-backed securities for which credit losses were not previously recorded.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2024
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 June 30, 2024 and December 31, 2023, 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. June 30, 2024 December 31, 2023 Carrying Total Fair Fair Value Measurements Categorized as: Carrying Total Fair Fair Value Measurements Categorized as: Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Financial assets: Fixed maturity securities: Municipal obligations $ 101 $ 101 $ — $ 101 $ — $ 99 $ 99 $ — $ 99 $ — Corporate obligations 742 742 — 742 — 745 745 — 726 19 Foreign obligations 105 105 105 — — 100 100 100 — — U.S. government obligations 105 105 105 — — 82 82 82 — — Residential mortgage-backed securities 253 253 — 253 — 250 250 — 250 — Commercial mortgage-backed securities 46 46 — 46 — 19 19 — 19 — Collateralized debt obligations 141 141 — 141 — 139 139 — 139 — Other asset-backed securities 241 241 — 164 77 303 303 — 235 68 Fixed maturity securities, pledged as collateral: U.S. government obligations 25 25 25 — — — — — — — Short-term — — — — — 27 27 27 — — Short term investments 314 314 313 1 — 426 426 421 5 — Other investments (1) 558 533 153 — — 475 463 77 — — Cash, cash equivalents and restricted cash 35 35 35 — — 28 28 27 2 — Other assets - Derivatives: Interest rate swaps—asset position 18 18 — — 18 25 25 — — 25 Warrants 1 1 — — 1 1 1 — — 1 Other assets-Loans 2 1 — — 1 2 2 — — 2 Variable interest entity assets: Fixed maturity securities: Corporate obligations, fair value option 2,010 2,010 — — 2,010 2,072 2,072 — — 2,072 Fixed maturity securities: Municipal obligations, available-for-sale 91 91 — 91 — 95 95 — 95 — Restricted cash 62 62 62 — — 246 246 246 — Loans 1,567 1,567 — — 1,567 1,663 1,663 — — 1,663 Derivative assets: Interest rate swaps—asset position 174 174 — 174 — 190 190 — 190 — Derivative assets: Currency swaps—asset position 34 34 — 34 — 36 36 — 36 — Total financial assets $ 6,626 $ 6,600 $ 797 $ 1,748 $ 3,675 $ 7,022 $ 7,010 $ 979 $ 1,795 $ 3,850 Financial liabilities: Long term debt, including accrued interest $ 1,015 $ 772 $ — $ 753 $ 19 $ 983 $ 697 $ — $ 679 $ 18 Other liabilities - Derivatives: Interest rate swaps—liability position 25 25 — 25 — 35 35 — 35 — FX forward — — — — — — — — — — Liabilities for net financial guarantees written (2) 229 488 — — 488 292 788 — — 788 Variable interest entity liabilities: Long-term debt 2,853 2,852 — 2,646 205 2,967 2,980 — 2,760 220 Derivative liabilities: Interest rate swaps—liability position 1,136 1,136 — 1,136 — 1,197 1,197 — 1,197 — Total financial liabilities $ 5,258 $ 5,273 $ — $ 4,561 $ 712 $ 5,474 $ 5,697 $ — $ 4,671 $ 1,026 (1) Excluded from the fair value measurement categories in the table above are investment funds of $380 and $386 as of June 30, 2024 and December 31, 2023, respectively, which are measured using NAV as a practical expedient. Also excluded from the fair value amounts in the table above are equity securities with a carrying value of $26 and $13 as of June 30, 2024 and December 31, 2023, respectively, that do not have readily determinable fair values and have carrying amounts determined using the measurement alternative. (2) The carrying value of net financial guarantees written includes financial guarantee amounts in 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.
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 2024 and 2023. 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 Investments Derivatives Investments Loans Total Three Months Ended June 30, 2024: Balance, beginning of period $ 87 $ 21 $ 2,070 $ 1,604 $ 3,782 Total gains/(losses) realized and unrealized: Included in earnings 7 (3) (51) 29 (19) Included in other comprehensive income 9 — 3 3 15 Settlements (26) — (12) (68) (106) Balance, end of period $ 77 $ 18 $ 2,010 $ 1,567 $ 3,672 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 $ 7 $ (3) $ (51) $ 29 $ (19) The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 9 $ — $ 3 $ 3 $ 15 Three Months Ended June 30, 2023: Balance, beginning of period $ 81 $ 31 $ 2,003 $ 1,856 $ 3,972 Total gains/(losses) realized and unrealized: Included in earnings — (5) (53) (66) (124) Included in other comprehensive income — — 14 50 64 Settlements — — (12) (69) (81) Balance, end of period $ 81 $ 25 $ 1,952 $ 1,772 $ 3,831 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 $ — $ (5) $ (53) $ (66) $ (124) The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ — $ — $ 14 $ 50 $ 64 Level 3 - Financial Assets and Liabilities Accounted for at Fair Value VIE Assets Investments Derivatives Investments Loans Total Six Months Ended June 30, 2024: Balance, beginning of period $ 87 $ 26 $ 2,072 $ 1,663 $ 3,848 Additions of VIEs consolidated — Total gains/(losses) realized and unrealized: Included in earnings 7 (8) (32) 49 16 Included in other comprehensive income 9 — (18) (14) (23) Purchases — — — — — Settlements (27) — (12) (132) (170) Balance, end of period $ 77 $ 18 $ 2,010 $ 1,567 $ 3,672 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 $ 7 $ (8) $ (32) $ 49 $ 16 The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 9 $ — $ (18) $ (14) $ (23) Six Months Ended June 30, 2023: Balance, beginning of period $ 79 $ 26 $ 1,828 $ 1,829 $ 3,762 Additions of VIEs consolidated — — — — — Total gains/(losses) realized and unrealized: Included in earnings 1 — 80 (7) 73 Included in other comprehensive income 3 — 57 92 152 Purchases — — — — — Settlements (1) — (12) (141) (155) Balance, end of period $ 81 $ 25 $ 1,952 $ 1,772 $ 3,831 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 $ — $ 80 $ (7) $ 73 The amount of total gains/(losses) included in other comprehensive income attributable to the change in unrealized gains or losses relating to assets and liabilities still held at the reporting date $ 3 $ — $ 57 $ 92 152
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: Three Months Ended June 30, 2024 Three Months Ended June 30, 2023 Net Net Gains Income (Loss) Other Net Net Gains Income (Loss) Other Total gains (losses) included in earnings for the period $ 7 $ (3) $ (22) $ — $ — $ (5) $ (119) $ — Changes in unrealized gains (losses) relating to financial instruments still held at the reporting date 9 (3) (22) — — (5) (119) — Six Months Ended June 30, 2024 Six Months Ended June 30, 2023 Net Net Gains Income (Loss) Other Net Net Gains Income (Loss) Other Total gains or losses included in earnings for the period $ 7 $ (8) $ 17 $ — $ 1 $ — $ 72 $ — Changes in unrealized gains or losses included in earnings relating to the assets and liabilities still held at the reporting date 9 (8) 17 — — — 72 —

Insurance Contracts (Tables)

Insurance Contracts (Tables)	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Insurance [Line Items]
Schedule of Loss And Loss Expense Reserves And Subrogation Recoverable Table [Table Text Block]	Ambac’s loss and loss expense reserves (“loss reserves”) are based on management’s on-going review of the insured portfolio. Below are the components of the loss and loss expense reserves and the subrogation recoverable asset at June 30, 2024 and December 31, 2023: June 30, 2024 December 31, 2023 Specialty Property and Casualty Legacy Financial Guarantee Specialty Property and Casualty Legacy Financial Guarantee Present Value of Expected Net Cash Flows Present Value of Expected Net Cash Flows Balance Sheet Line Item Gross Loss Claims and Recoveries Unearned Gross Loss Gross Loss Claims and Recoveries Unearned Gross Loss Loss and loss expense reserves $ 286 $ 669 $ (51) $ (14) $ 890 $ 197 $ 779 $ (55) $ (28) $ 893 Subrogation recoverable — 7 (136) — (128) — 1 (139) — (137) Totals $ 286 $ 676 $ (186) $ (14) $ 762 $ 197 $ 780 $ (194) $ (28) $ 756
Premiums Receivable by Risk Classification Code [Table Text Block]	Below is the amortized cost basis of financial guarantee premium receivables by risk classification code and asset class as of June 30, 2024 and December 31, 2023: Surveillance Categories as of June 30, 2024 Surveillance Categories as of December 31, 2023 Type of Guaranteed Bond I IA II III IV Total I IA II III IV Total Public Finance: Housing revenue $ 127 $ 3 $ 5 $ — $ — $ 134 $ 131 $ 3 $ 5 $ — $ — $ 139 Other 1 — — — — 1 1 — — — — 1 Total Public Finance 128 3 5 — — 135 133 3 5 — — 140 Structured Finance: Mortgage-backed and home equity — — — — 10 11 — — — — 11 12 Student loan — — — 3 1 4 — — — 7 — 7 Other 3 — — — — 3 4 — — — — 4 Total Structured Finance 3 — — 3 10 17 4 — — 7 11 22 International: Sovereign/sub-sovereign 58 5 — — — 63 51 13 — — — 64 Investor-owned and public utilities 16 — — — — 16 18 — — — — 18 Other 3 — — — — 3 3 — — — — 3 Total International 77 5 — — — 82 72 13 — — — 85 Total (1) (2) $ 209 $ 8 $ 5 $ 3 $ 10 $ 235 $ 210 $ 16 $ 5 $ 7 $ 11 $ 248 (1) Excludes specialty property and casualty premium receivables of $85 and $46 at June 30, 2024 and December 31, 2023, respectively. (2) The underwriting origination dates for all policies included are greater than five years prior to the current reporting date.
Premium Receivable, Allowance for Credit Loss [Table Text Block]	Below is the gross premium receivable roll-forward, net of the allowance for credit losses, for the affected periods: Six Months Ended June 30, 2024 2023 Beginning premiums receivable 290 269 Premiums written on new business, net of commissions 159 83 Premium receipts (134) (90) Adjustments for changes in expected and contractual cash flows for contracts (1) (2) 6 Accretion of premium receivable discount for contracts 4 4 Changes in allowance for credit losses 1 1 Other adjustments (including foreign exchange) (2) (1) 4 Ending premium receivable (3) 317 276 (1) Adjustments for changes in expected and contractual cash flows are primarily due to inflation indexation and reductions in insured exposure as a result of early policy terminations and unscheduled principal paydowns for financial guarantee policies. (2) Includes foreign exchange gains/(losses) of $(1) and $4 for 2024 and 2023 , respectively. (3) Premium receivable includes premiums to be received in foreign denominated currencies most notably in British Pounds and Euros. At June 30, 2024 and 2023, premium receivables include British Pounds of $70 (£55) and $76 (£60), respectively, and Euros of $12 (€11) and $14 (€12), respectively.	Below is a rollforward of the premium receivable allowance for credit losses as of June 30, 2024 and 2023: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Beginning balance $ 3 $ 5 $ 4 $ 5 Current period provision (benefit) — (1) (2) (1) Write-offs of the allowance — — — — Recoveries of previously written-off amounts — — — — Ending balance (1) $ 3 $ 5 $ 3 $ 5 (1) At June 30, 2024 and 2023, $1 and $0 of premiums were past due.
Summary of Loss Reserve Roll-Forward, Net of Subrogation Recoverable and Reinsurance	Below is the loss and loss reserve expense roll-forward, net of subrogation recoverable and reinsurance, for the affected periods: Six Months Ended June 30, 2024 2023 Beginning gross loss and loss expense reserves $ 756 $ 534 Reinsurance recoverable 186 115 Beginning balance of net loss and loss expense reserves 570 419 Losses and loss expenses (benefit): Current year 40 8 Prior years (23) 18 Total (1) 17 25 Loss and loss expenses paid (recovered): Current year 3 1 Prior years 63 (136) Total 66 (135) Foreign exchange effect — — Ending net loss and loss expense reserves 520 580 Reinsurance recoverable (2) 242 144 Ending gross loss and loss expense reserves $ 762 $ 724 (1) Total losses and loss expenses (benefit) includes $(98) and $(45) for the six months ended June 30, 2024 and 2023, respectively, related to ceded reinsurance. (2) Represents reinsurance recoverable on future loss and loss expenses. Additionally, the Balance Sheet line "Reinsurance recoverable on paid and unpaid losses" includes reinsurance recoverables (payables) of $35 and $5 as of June 30, 2024 and 2023, respectively, related to previously presented loss and loss expenses and subrogation.
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 June 30, 2024 and December 31, 2023, excluding consolidated VIEs. Gross par exposures include capital appreciation bonds which are reported at the par amount at the time of issuance of the insurance policy as opposed to the current accreted value of the bond. The weighted average risk-free rate used to discount loss reserves at June 30, 2024 and December 31, 2023,was 4.4% and 4.6%, respectively. Surveillance Categories as of June 30, 2024 I IA II III IV V Total Number of policies 24 3 10 11 91 4 143 Remaining weighted-average contract period (in years) (1) 5 18 12 11 12 8 11 Gross insured contractual payments outstanding: Principal $ 219 $ 194 $ 439 $ 269 $ 1,439 $ 21 $ 2,581 Interest 18 182 253 99 573 16 1,141 Total $ 237 $ 376 $ 692 $ 368 $ 2,012 $ 37 $ 3,722 Gross undiscounted claim liability $ — $ 9 $ 39 $ 231 $ 809 $ 37 $ 1,126 Discount, gross claim liability — (2) (7) (77) (359) (8) (452) Gross claim liability before all subrogation and before reinsurance — 7 32 155 450 29 674 Less: Gross other subrogation (2) (13) (3) (1) (25) (211) (11) (263) Discount, other subrogation 2 — — 4 67 3 77 Discounted other subrogation, before reinsurance (10) (3) — (21) (144) (8) (186) Gross claim liability, net of all subrogation and discounts, before reinsurance (10) 4 32 134 307 21 487 Less: Unearned premium revenue — (2) (4) 2 (9) (1) (14) Plus: Loss expense reserves 1 1 — — 1 — 3 Gross loss and loss expense reserves $ (9) $ 2 $ 28 $ 136 $ 298 $ 21 $ 476 Reinsurance recoverable reported on Balance Sheet (3) $ — $ — $ 8 $ 14 $ 4 $ — $ 26 (1) Remaining weighted-average contract period is weighted based on projected gross claims over the lives of the respective policies. (2) Other subrogation represents subrogation related to excess spread and other contractual cash flows on public finance and structured finance transactions, including RMBS. (3) Reinsurance recoverable reported on the Balance Sheet includes reinsurance recoverables of $26 related to future loss and loss expenses and $0 related to presented loss and loss expenses and subrogation. Surveillance Categories as of December 31, 2023 I IA II III IV V Total Number of policies 18 8 9 13 88 5 141 Remaining weighted-average contract period (in years) (1) 9 9 13 13 12 7 12 Gross insured contractual payments outstanding: Principal $ 429 $ 1,084 $ 430 $ 394 $ 1,473 $ 27 $ 3,838 Interest 75 328 262 139 600 17 1,421 Total $ 505 $ 1,412 $ 692 $ 534 $ 2,073 $ 44 $ 5,259 Gross undiscounted claim liability $ 1 $ 19 $ 41 $ 324 $ 772 $ 44 $ 1,202 Discount, gross claim liability — (2) (7) (86) (323) (8) (426) Gross claim liability before all subrogation and before reinsurance 1 17 34 239 450 36 777 Less: Gross other subrogation (2) (13) (2) — (27) (208) (11) (263) Discount, other subrogation 2 — — 4 60 3 69 Discounted other subrogation, before reinsurance (11) (2) — (23) (149) (8) (194) Gross claim liability, net of all subrogation and discounts, before reinsurance (10) 15 34 215 301 28 583 Less: Unearned premium revenue — (12) (4) — (10) (1) (28) Plus: Loss expense reserves — 3 — — 1 — 4 Gross loss and loss expense reserves $ (10) $ 6 $ 30 $ 215 $ 292 $ 27 $ 559 Reinsurance recoverable reported on Balance Sheet (4) $ 1 $ — $ 8 $ 18 $ 3 $ — $ 30 (1) Remaining weighted-average contract period is weighted based on projected gross claims over the lives of the respective policies. (2) Other subrogation represents subrogation related to excess spread and other contractual cash flows on public finance and structured finance transactions, including RMBS. (3) Reinsurance recoverable reported on the Balance Sheet includes reinsurance recoverables of $30 related to future loss and loss expenses and $(1) related to presented loss and loss expenses and subrogation
Summary of Rollforward of RMBS Subrogation, by Estimation Approach	.
Effects of Reinsurance	The effect of reinsurance on premiums written and earned was as follows: Three Months Ended June 30, 2024 2023 Written Earned Written Earned Direct $ 93 $ 79 $ 55 $ 52 Assumed 20 17 — — Ceded 79 64 100 37 Net premiums $ 34 $ 33 $ (45) $ 15 Six Months Ended June 30, 2024 2023 Written Earned Written Earned Direct $ 174 $ 154 $ 115 $ 98 Assumed 38 33 — — Ceded 150 121 142 69 Net premiums $ 62 $ 66 $ (27) $ 29 The following table summarizes net premiums earned by location of risk: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 United States $ 30 $ 12 $ 60 $ 23 United Kingdom 3 3 5 5 Other international — 1 1 1 Total $ 33 $ 15 $ 66 $ 29
Financial Guarantee Insurance Contracts, Premium Received over Contract Period	The following table summarizes the future Legacy Financial Guarantee gross undiscounted premiums to be collected and future premiums earned, net of reinsurance at June 30, 2024: Future Premiums Collected (1) Future (2) Three months ended: September 30, 2024 $ 7 $ 4 December 31, 2024 5 4 Twelve months ended: December 31, 2025 25 15 December 31, 2026 24 15 December 31, 2027 23 15 December 31, 2028 22 14 Five years ended: December 31, 2033 92 54 December 31, 2038 54 27 December 31, 2043 25 9 December 31, 2048 12 4 December 31, 2053 2 1 December 31, 2058 — — Total $ 293 $ 163 (1) Future premiums to be collected are undiscounted, gross of allowance for credit losses, and are used to derive the discounted premium receivable asset recorded on Ambac's balance sheet. (2) Future premiums to be earned, net of reinsurance relate to the unearned premiums 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 the Notes to Consolidated Financial Statements included in Ambac's Annual Report on Form 10-K for the year ended December 31, 2023. 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 may result in different 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.
Reinsurance Recoverable, Credit Quality Indicator	The following table sets forth our three most significant reinsurers by amount of reinsurance recoverable as of June 30, 2024. Reinsurers Type of Insurance Rating (1) Reinsurance Recoverable (2) Unsecured Recoverable (3) General Reinsurance Company Specialty P&C A++ $ 123 $ 104 QBE Insurance Corporation Specialty P&C A 37 37 Assured Guaranty Re Ltd. Financial AA 22 — All other reinsurers 94 35 Total recoverables $ 277 $ 176 (1) Represents financial strength ratings from S&P for financial guarantee reinsurers and AM Best for specialty P&C reinsurers. (2) Represents reinsurance recoverables on paid and unpaid losses. Unsecured amounts from QBE Insurance Corporation is also supported by an unlimited, uncapped indemnity from Enstar Holdings (US). (3) Reinsurance recoverables reduced by ceded premiums payables due to reinsurers, letters of credit, and collateral posted for the benefit of Ambac.

Derivative Instruments (Tables)

Derivative Instruments (Tables)	6 Months Ended
	Jun. 30, 2024
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 June 30, 2024 and December 31, 2023: June 30, 2024 December 31, 2023 Gross Gross Net Amounts Gross Amount Net Gross Gross Net Amounts Gross Amount Net Other assets: Interest rate swaps $ 18 $ — $ 18 $ — $ 18 $ 25 $ — $ 25 $ — $ 25 Warrants 1 — 1 — 1 1 — 1 — 1 Total non-VIE derivative assets $ 18 $ — $ 18 $ — $ 18 $ 26 $ — $ 26 $ — $ 26 Other liabilities: Interest rate swaps $ 25 $ — $ 25 $ 25 $ — $ 35 $ — $ 35 $ 35 $ — FX forward — — — — — — — — — — Total non-VIE derivative liabilities $ 26 $ — $ 26 $ 25 $ — $ 35 $ — $ 35 $ 35 $ — Variable interest entities assets: Derivative and other assets: Interest rate swaps $ 174 $ — $ 174 $ 174 $ — $ 190 $ — $ 190 $ 190 $ — Currency swaps 34 — 34 34 — 36 — 36 36 — Total VIE derivative assets $ 208 $ — $ 208 $ 208 $ — $ 226 $ — $ 226 $ 226 $ — Variable Interest Entities Derivative Liabilities: Interest rate swaps $ 1,136 $ — $ 1,136 $ — $ 1,136 $ 1,197 $ — $ 1,197 $ — $ 1,197 Total VIE derivative liabilities $ 1,136 $ — $ 1,136 $ — $ 1,136 $ 1,197 $ — $ 1,197 $ — $ 1,197
Summary of Location and Amount of Gains and Losses of Derivative Contracts	The following tables summarize the location and amount of gains and losses of derivative contracts in the Unaudited Consolidated Statements of Total Comprehensive Income (Loss) for the three and six months ended June 30, 2024 and 2023: Location of Gain (Loss) Amount of Gain (Loss) Recognized in Consolidated Statement of Total Comprehensive Income (Loss) Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Non-VIE derivatives: Interest rate swaps Net gains (losses) on derivative contracts 1 1 2 (3) Warrants Net gains (losses) on derivative contracts — — — — FX Forward Net gains (losses) on derivative contracts — — — — Total Non-VIE derivatives $ — $ — 2 (3) Variable Interest Entities: Currency swaps Income (loss) on variable interest entities $ — $ (1) 2 (3) Interest rate swaps Income (loss) on variable interest entities 43 97 57 (2) Total Variable Interest Entities 44 96 59 (5) Total derivative contracts $ 44 $ 97 $ 61 $ (8)
Summary of Notional Amounts of AFS's Trading Derivative Products	As of June 30, 2024 and December 31, 2023, the notional amounts of AFS’s derivatives are as follows: Notional Type of Derivative June 30, December 31, Interest rate swaps—pay-fixed/receive-variable $ 140 $ 141 Interest rate swaps—receive-fixed/pay-variable 159 167
Variable Interest Entity, Primary Beneficiary [Member]
Summary of Notional Amounts of AFS's Trading Derivative Products	The notional amounts for VIE derivatives outstanding as of June 30, 2024 and December 31, 2023, were as follows: Notional Type of VIE Derivative June 30, December 31, Interest rate swaps—receive-fixed/pay-variable $ 1,648 $ 1,662 Interest rate swaps—pay-fixed/receive-variable 820 864 Currency swaps 136 149

Intangible Assets (Tables)

Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2024
Insurance Intangible Asset [Member]
Finite-Lived Intangible Assets [Line Items]
Schedule of Finite-Lived Intangible Assets	ntangible assets and accumulated amortization are included in the Consolidated Balance Sheets, as shown below. June 30, December 31, Finite-lived Intangible Assets: Insurance intangible: Gross carrying value $ 1,256 $ 1,258 Accumulated amortization 1,030 1,013 Net insurance intangible asset 226 245 Other intangibles: Gross carrying value 57 57 Accumulated amortization 12 10 Net other intangible assets 45 47 Total finite-lived intangible assets 271 292 Indefinite-lived Intangible Assets: Insurance licenses 14 14 Total intangible assets $ 285 $ 307

Special Purpose Entities, Inclu

Special Purpose Entities, Including Variable Interest Entities (Tables)	6 Months Ended
	Jun. 30, 2024
Debt Disclosure [Abstract]
Schedule of Variable Interest Entities Assets and Liabilities [Table Text Block]	The following table summarizes the carrying values of assets and liabilities, along with other supplemental information related to FG VIEs that are consolidated because of financial guarantees of Ambac UK and AAC: June 30, 2024 December 31, 2023 Ambac UK Ambac Assurance Total VIEs Ambac UK Ambac Assurance Total VIEs ASSETS: Fixed maturity securities, at fair value: Corporate obligations, fair value option $ 2,010 $ — $ 2,010 $ 2,072 $ — $ 2,072 Municipal obligations, available-for-sale (1) — 91 91 — 95 95 Total LFG VIE fixed maturity securities, at fair value 2,010 91 2,101 2,072 95 2,167 Restricted cash 61 1 62 245 1 246 Loans, at fair value (2) 1,567 — 1,567 1,663 — 1,663 Derivative assets 208 — 208 226 — 226 Other assets, including contract assets 93 2 95 90 2 92 Total LFG VIE assets $ 3,939 $ 94 $ 4,033 $ 4,296 $ 98 $ 4,394 LIABILITIES: Long-term debt: Long-term debt, at fair value (3) $ 2,599 $ — $ 2,599 $ 2,710 $ — $ 2,710 Long-term debt, at par less unamortized discount 97 156 253 99 159 258 Total long-term debt 2,696 156 2,853 2,808 159 2,967 Derivative liabilities 1,136 — 1,136 1,197 — 1,197 Cash collateral payable 52 — 52 235 — 235 Other liabilities 6 1 7 4 1 5 Total LFG VIE liabilities $ 3,890 $ 157 $ 4,048 $ 4,244 $ 160 $ 4,404 Number of LFG VIEs consolidated 4 2 6 4 2 6
Variable Interest Entity [Line Items]
Components of VIE Gain (Loss) [Table Text Block]	The following schedule details the components of Income (loss) on variable interest entities for the affected periods: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Net change in fair value of VIE assets and liabilities reported under the fair value option $ — $ — $ 1 $ 2 Less: Credit risk changes of fair value option long-term debt reported through other comprehensive income (loss) — 1 — 1 Net change in fair value of VIE assets and liabilities reported in earnings under the fair value option 1 — 2 3 Investment income (loss) 2 3 5 5 Contract revenue 3 — 8 — Net realized investment gains (losses) on available-for-sale securities — — — — Interest expense on long-term debt carried at par less unamortized cost (4) (3) (6) (8) Other expenses (3) — (7) — Gain (loss) from consolidating VIEs — — — — Income (loss) on variable interest entities $ — $ — $ 2 $ (1)
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 June 30, 2024 and December 31, 2023: June 30, 2024: December 31, 2023: Carrying Value of Assets and Liabilities Carrying Value of Assets and Liabilities Maximum (1) Insurance (2) Insurance (3) Net Derivative (4) Maximum (1) Insurance (2) Insurance (3) Net Derivative (4) Global structured finance: Mortgage-backed—residential $ 2,224 $ 123 $ 409 $ — $ 2,391 $ 135 $ 432 $ — Other consumer asset-backed 365 3 135 — 540 5 200 — Other 418 2 2 — 433 2 2 — Total global structured finance 3,007 127 546 — 3,364 141 634 — Global public finance 17,101 204 196 — 17,498 209 202 — Total $ 20,109 $ 331 $ 742 $ — $ 20,861 $ 351 $ 836 $ — (1) Maximum exposure to loss represents the maximum future payments of principal and interest on insured obligations and derivative contracts. 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 included in “Premium receivables” and “Subrogation recoverable” for financial guarantee insurance contracts on Ambac’s Consolidated Balance Sheets. (3) Insurance liabilities represent the amount included in “Loss and loss expense reserves” and “Unearned premiums” for financial guarantee insurance contracts on Ambac’s Consolidated Balance Sheets. (4) Net derivative assets (liabilities) represent the fair value recognized on interest rate swaps on Ambac’s Consolidated Balance Sheets.
Schedule of Variable Interest Entities Assets and Liabilities [Table Text Block]	The following table summarizes the carrying values of assets and liabilities, along with other supplemental information related to FG VIEs that are consolidated because of financial guarantees of Ambac UK and AAC: June 30, 2024 December 31, 2023 Ambac UK Ambac Assurance Total VIEs Ambac UK Ambac Assurance Total VIEs ASSETS: Fixed maturity securities, at fair value: Corporate obligations, fair value option $ 2,010 $ — $ 2,010 $ 2,072 $ — $ 2,072 Municipal obligations, available-for-sale (1) — 91 91 — 95 95 Total LFG VIE fixed maturity securities, at fair value 2,010 91 2,101 2,072 95 2,167 Restricted cash 61 1 62 245 1 246 Loans, at fair value (2) 1,567 — 1,567 1,663 — 1,663 Derivative assets 208 — 208 226 — 226 Other assets, including contract assets 93 2 95 90 2 92 Total LFG VIE assets $ 3,939 $ 94 $ 4,033 $ 4,296 $ 98 $ 4,394 LIABILITIES: Long-term debt: Long-term debt, at fair value (3) $ 2,599 $ — $ 2,599 $ 2,710 $ — $ 2,710 Long-term debt, at par less unamortized discount 97 156 253 99 159 258 Total long-term debt 2,696 156 2,853 2,808 159 2,967 Derivative liabilities 1,136 — 1,136 1,197 — 1,197 Cash collateral payable 52 — 52 235 — 235 Other liabilities 6 1 7 4 1 5 Total LFG VIE liabilities $ 3,890 $ 157 $ 4,048 $ 4,244 $ 160 $ 4,404 Number of LFG VIEs consolidated 4 2 6 4 2 6

Revenue Recognition and Deferre

Revenue Recognition and Deferred Revenue (Tables)	6 Months Ended
	Jun. 30, 2024
Revenue Recognition and Deferred Revenue [Abstract]
Disaggregation of Revenue	Insurance Distribution revenues recognized, disaggregated by policy type, were as follows: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Employer stop loss $ 2 $ 2 $ 7 $ 7 Affinity products 5 5 10 10 Commercial auto 3 2 7 5 Marine 1 1 2 2 Professional liability 2 — 4 — Other — — — — Total $ 13 $ 10 $ 31 $ 25
Contract with Customer, Contract Asset, Contract Liability, and Receivable	The balances of contract assets and contract liabilities with customers were as follows: June 30, 2024 December 31, 2023 Contract assets 101 95 Contract liabilities — 1

Comprehensive Income (Tables)

Comprehensive Income (Tables)	6 Months Ended
	Jun. 30, 2024
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: Three Months Ended June 30, 2024: Three Months Ended June 30, 2023: Unrealized Gains (1) Amortization of Postretirement Benefit (1) Gain (Loss) on Foreign Currency (1) Credit Risk Changes of Fair Value Option Liabilities (1) (2) Total Unrealized Gains (1) Amortization of Postretirement Benefit (1) Gain (Loss) on Foreign Currency (1) Credit Risk Changes of Fair Value Option Liabilities (1) (2) Total Beginning Balance $ (27) $ 5 $ (152) $ (1) $ (175) $ (54) $ 6 $ (168) $ (1) $ (217) Other comprehensive income (loss) before reclassifications 8 — 1 — 9 (15) — 21 — 6 Amounts reclassified from accumulated other comprehensive income (loss) (4) (5) — — (9) 3 — — — 2 Net current period other comprehensive income (loss) 4 (5) 1 — — (13) — 21 — 8 Ending Balance $ (23) $ — $ (151) $ (1) $ (175) $ (67) $ 6 $ (147) $ (1) $ (209) Six Months Ended June 30, 2024 Six Months Ended June 30, 2023 Unrealized Gains (1) Amortization of Postretirement Benefit (1) Gain (Loss) on Foreign Currency (1) Credit Risk Changes of Fair Value Option Liabilities (1) (2) Total Unrealized Gains (1) Amortization of Postretirement Benefit (1) Gain (Loss) on Foreign Currency (1) Credit Risk Changes of Fair Value Option Liabilities (1) (2) Total Beginning Balance $ (20) $ 5 $ (144) $ (1) $ (160) $ (71) $ 3 $ (184) $ (1) $ (253) Other comprehensive income before reclassifications 1 — (7) — (5) (1) 3 37 — 39 Amounts reclassified from accumulated other comprehensive income (5) (5) — — (10) 6 (1) — — 5 Net current period other comprehensive income (3) (5) (7) — (15) 5 2 37 — 44 Ending Balance $ (23) $ — $ (151) $ (1) $ (175) $ (67) $ 6 $ (147) $ (1) $ (209) (1) All amounts are net of tax and noncontrolling interest. Amounts in parentheses indicate reductions to Accumulated Other Comprehensive Income. (2) Represents the changes in fair value attributable to instrument-specific credit risk of liabilities for which the fair value option is elected.
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, shown in the above rollforward tables, for the affected periods: Details about Accumulated Amount Reclassified from Affected Line Item in the Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Unrealized Gains (Losses) on Available-for-Sale Securities $ (4) $ 3 $ (4) $ 8 Net realized investment gains (losses) — (1) — (2) Provision for income taxes $ (4) $ 3 $ (5) $ 6 Net of tax and noncontrolling interest Amortization of Postretirement Benefit Prior service cost $ — $ — $ — $ — Other income Actuarial (losses) — — — — Other income Curtailment gain (5) — (5) — Other income (5) — (5) (1) Total before tax — — — — Provision for income taxes $ (5) $ — $ (5) $ (1) Net of tax and noncontrolling interest Credit Risk Changes of Fair Value Option Liabilities $ — $ (1) $ — $ — Credit risk changes of fair value option liabilities — — — — Provision for income taxes $ — $ — $ — $ — Net of tax and noncontrolling interest Total reclassifications for the period $ (9) $ 2 $ (9) $ 5 Net of tax and noncontrolling interest

Net Income Per Share (Tables)

Net Income Per Share (Tables)	6 Months Ended
	Jun. 30, 2024
Earnings Per Share [Abstract]
Reconciliation of Common Shares Used for Basic and Diluted Earnings Per Share	The following table provides a reconciliation of the weighted average shares denominator used for basic net income per share to the denominator used for diluted net income per share: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Basic weighted average shares outstanding denominator 46,209,250 45,757,234 46,019,145 45,661,288 Effect of potential dilutive shares : Restricted stock units — — 158,132 — Performance stock units (1) — — 391,585 — Diluted weighted average shares outstanding denominator 46,209,250 45,757,234 46,568,862 45,661,288 Anti-dilutive shares excluded from the above reconciliation: Warrants — — — — Restricted stock units 471,541 556,602 44,362 555,981 Performance stock units (1) 464,272 667,365 — 667,365 (1) Performance stock units are reflected based on the performance metrics through the balance sheet date. Vesting of these units is contingent upon meeting certain performance metrics. Although a portion of these performance metrics have been achieved as of the respective period end, it is possible that awards may no longer meet the metric at the end of the performance period.
Schedule of Earnings Per Share, Basic and Diluted	The following table provides a reconciliation of net income attributable to common stockholders to the numerator in the basic and diluted earnings per share calculation, together with the resulting earnings per share amounts: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Net income (loss) attributable to common stockholders $ (1) $ (13) $ 19 (47) Adjustment to redemption value (ASC 480) — — — — Numerator of basic and diluted EPS $ (1) $ (13) $ 19 (47) Per Share: Basic $ (0.02) $ (0.29) $ 0.42 $ (1.02) Diluted $ (0.02) $ (0.29) $ 0.41 $ (1.02)

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2024
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 2015 New York City 2018 United Kingdom 2020 Italy 2019
Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]	U.S. and foreign components of pre-tax income (loss) were as follows: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 U.S. $ (11) $ (18) $ (1) $ (66) Foreign 13 7 28 26 Total $ 2 $ (11) $ 27 $ (40) 1
Schedule of Components of Income Tax Expense (Benefit)	The components of the provision for income taxes were as follows: Three Months Ended June 30, Six Months Ended June 30, 2024 2023 2024 2023 Current taxes U. S. federal $ — $ 1 $ — $ 1 U.S. state and local — — — — Foreign 2 — 7 2 Total Current taxes 2 2 7 4 Deferred taxes Foreign — — 1 2 Total Deferred taxes — — 1 2 Provision for income taxes $ 2 $ 2 $ 7 $ 6

Business and Basis of Present_3

Business and Basis of Presentation Background and Business Description - Additional Information (Details)	6 Months Ended
	Jun. 30, 2024 level3FinancialInstruments
Background And Basis Of Presentation [Line Items]
Entity Incorporation, Date of Incorporation	Apr. 29, 1991
Number of Reportable Segments	3
Background and Business Description	1. BUSINESS AND BASIS OF PRESENTATION Business The following description provides an update of Note 1. Background and Business Description and Note 2. Basis of Presentation and Significant Accounting Policies in the Notes to the Consolidated Financial Statements included in Part II, Item 8 in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023, and should be read in conjunction with the complete descriptions provided in the Form 10-K. Capitalized terms used, but not defined herein, and in the other footnotes to the Consolidated Financial Statements included in this Quarterly Report on Form 10-Q shall have the meanings ascribed thereto in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. Ambac Financial Group, Inc. (“AFG”), headquartered in New York City, is a specialty insurance holding company incorporated in the state of Delaware on April 29, 1991. References to “Ambac,” the “Company,” “we,” “our,” and “us” are to AFG and its subsidiaries, as the context requires. Ambac's principal businesses include: • Specialty Property & Casualty Insurance — Ambac's Specialty Property & Casualty Insurance program business. Currently includes six carriers (collectively, “Everspan”). Everspan carriers have an A.M. Best rating of 'A-' (Excellent) that was affirmed on June 13, 2024. • Insurance Distribution — Ambac's specialty property and casualty ("P&C") insurance distribution business, which could include Managing General Agents and Underwriters (collectively "MGAs"), insurance brokers, and other distribution businesses. At June 30, 2024 Ambac's insurance distribution platform includes five businesses that operate in the following lines of business: accident and health, specialty commercial automobile insurance for specific "for-hire" auto clauses, marine and international risk and professional liability. • Legacy Financial Guarantee Insurance — Ambac's legacy financial guarantee business includes the activities of Ambac Assurance Corporation ("AAC") and its wholly owned subsidiaries, including Ambac Assurance UK Limited (“Ambac UK”) and Ambac Financial Services LLC ("AFS"). Both AAC and Ambac UK (the "Legacy Financial Guarantee Companies") have financial guarantee insurance portfolios that have been in runoff since 2008. AFS provided interest rate derivatives to financial guarantee customers and used derivatives to hedge interest rate risk in AAC's insurance and investment portfolios. AFS' remaining derivative positions include a limited number of legacy customer swaps and their associated hedges. The Company reports these three business operations as segments; see Note 2. Segment Information for further information.

Business and Basis of Present_4

Business and Basis of Presentation FX gain (loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Foreign Currency Transaction Gain (Loss), before Tax			$ (1)	$ (3)
Gain (Loss) on Investments [Member]
Foreign Currency Transaction Gain (Loss), before Tax	$ (1)	$ (2)	$ 0	$ (4)

Business and Basis of Present_5

Business and Basis of Presentation Additional Information (Details) - USD ($)	3 Months Ended			6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Stockholders' Equity Attributable to Noncontrolling Interest	$ 51,000,000			$ 51,000,000		$ 53,000,000
Preferred Stock, Shares Issued	0			0		0
Redeemable Noncontrolling Interest, Equity, Carrying Amount	$ 17,000,000	$ 20,000,000		$ 17,000,000	$ 20,000,000	$ 17,000,000	$ 20,000,000
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest				1,000,000	1,000,000
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders				(1,000,000)	(1,000,000)
Redeemable Noncontrolling Interest, Equity, Redemption Value	17,000,000			17,000,000
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	0	0		(1,000,000)	(1,000,000)
Noncontrolling Interest, Change in Redemption Value	$ 0	$ 0	$ 0	0	0
Number of Variable Interest Entities Consolidated During the Period	0	0
Temporary Equity, Accretion to Redemption Value, Adjustment				0	0
Business Combination, Acquisition of Less than 100 Percent, Noncontrolling Interest, Fair Value	$ 0	$ 0		0	$ 0
Retained Earnings [Member]
Derivative [Line Items]
Noncontrolling Interest, Change in Redemption Value	$ 0	$ 0		$ 0

Business and Basis of Present_6

Business and Basis of Presentation Supplemental Cash Flow information (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Cash and Cash Equivalents, at Carrying Value	$ 24	$ 24	$ 33
Income Taxes Paid		7	6
Restricted Cash	11	11	10	$ 12
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	97	97	309	274	$ 61
Securities acquired (transferred) in transactions related to Puerto Rico restructurings	0		(1)
Securities acquired (transferred) in connection with financial guarantee commutations		(65)
Long-term Debt [Member]
Interest Paid, Including Capitalized Interest, Operating and Investing Activities		0	50
Variable Interest Entity, Primary Beneficiary [Member]
Restricted Cash	$ 62	$ 62	$ 266	$ 246

Business and Basis of Present_7

Business and Basis of Presentation (Details)		6 Months Ended
	Jul. 31, 2024 USD ($) level3FinancialInstruments	Mar. 31, 2025 USD ($)
Business Combination, Total Consideration	$ 278,000,000
Business Combination, Consideration Paid in Cash	$ 249,000,000
Subsequent Event
Business Acquisition, Percentage of Voting Interests Acquired	60%
Business Combination, Percentage Ownership Retained by Rollover Shareholders	20%
Business Combination, Number of Shares Issued for Beat Acquisition | level3FinancialInstruments	2,216,023
Business Combination, AAC Cash Consideration for Beat Acquisition	$ 65,000,000
Business Combination, Credit Facility Cash Used for Beat Acquisition	150,000,000
Business Combination, FX Forward Rate Lock	$ 1.2662
Business Disposal, Cash Expected to be Received		$ 420,000,000
Business Disposal, Termination Fee		22,000,000
Business Disposal, Potential Out Of Pocket Expense Reimbursement		$ 6,000,000
Business Disposal, Percent of Common Shares Issued in Connection with Disposal		9.90%
Business Disposal, Warrant Strike Price in Connection with Disposal		$ 18.50
Business Disposal, Carrying Value of AAC		939,000,000
Business Disposal, AAC Accumulated Other Comprehensive Loss		$ (168,000,000)
Business Disposal, Life of Warrants Issued in Connection with AAC Disposal		6 years 6 months

Segment Reporting (Details)

Segment Reporting (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) level3FinancialInstruments	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Segment Reporting, Revenue Reconciling Item [Line Items]
Number of Reportable Segments | level3FinancialInstruments			3
Revenues	$ 105,000	$ 62,000	$ 207,000	$ 120,000
Policyholder Benefits and Claims Incurred, Net	18,000	7,000	16,000	25,000
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	2,000	(11,000)	27,000	(40,000)
Provision for income taxes	2,000	2,000	7,000	6,000
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(1,000)	(13,000)	20,000	(46,000)
Premiums Earned, Net	33,000	15,000	66,000	29,000
Net Investment Income	36,000	35,000	78,000	69,000
Amortization of Intangible Assets	8,000	7,000	21,000	13,000
Interest Expense	16,000	16,000	32,000
Total assets	8,184,000	8,132,000	8,184,000	8,132,000	$ 8,428,000
Premiums Written, Net	34,000	(45,000)	62,000	(27,000)
Derivative, Gain (Loss) on Derivative, Net	0	0	2,000	(3,000)
Insurance Commissions and Fees	13,000	10,000	31,000	25,000
Losses and loss adjustment expenses (benefit)			16,000	25,000
Other Cost and Expense, Operating	47,000	36,000	82,000	72,000
Insurance Commissions	8,000	6,000	18,000	14,000
Depreciation	1,000	0	1,000	1,000
Benefits, Losses and Expenses	103,000	73,000	180,000	160,000
Net Income (Loss) Attributable to Nonredeemable Noncontrolling Interest	0	0	(1,000)	(1,000)
Net income attributable to common shareholders	(1,000)	(13,000)	19,000	(47,000)
Realized Investment Gains (Losses)	4,000	(3,000)	4,000	(8,000)
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	3,000	2,000	6,000	4,000
Other income Items	15,000	3,000	21,000	4,000
Deferred Policy Acquisition Costs, Amortization Expense	5,000	1,000	10,000	3,000
Financial Guarantee
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	53,000	39,000	107,000	71,000
Policyholder Benefits and Claims Incurred, Net	(5,000)	2,000
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	13,000	(8,000)	38,000	(40,000)
Premiums Earned, Net	6,000	8,000	13,000	14,000
Net Investment Income	32,000	32,000	70,000	63,000
Amortization of Intangible Assets	7,000	6,000	18,000	11,000
Interest Expense	16,000	16,000	32,000	32,000
Total assets	7,100,000	7,376,000	7,100,000	7,376,000
Derivative, Gain (Loss) on Derivative, Net	1,000	1,000	2,000	(3,000)
Losses and loss adjustment expenses (benefit)			(26,000)	15,000
Other Cost and Expense, Operating	22,000	23,000	44,000	52,000
Depreciation	0	0	0	1,000
Benefits, Losses and Expenses	40,000	47,000	69,000	111,000
Realized Investment Gains (Losses)	(1,000)	(3,000)	0	(8,000)
Other income Items	16,000	2,000	21,000	4,000
Deferred Policy Acquisition Costs, Amortization Expense	0	0	0	0
Specialty Property & Casualty Program
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	32,000	11,000	61,000	20,000
Policyholder Benefits and Claims Incurred, Net	23,000	6,000
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(1,000)	0	1,000	(1,000)
Premiums Earned, Net	27,000	8,000	53,000	15,000
Net Investment Income	1,000	1,000	3,000	2,000
Total assets	713,000	395,000	713,000	395,000
Losses and loss adjustment expenses (benefit)			42,000	10,000
Other Cost and Expense, Operating	5,000	4,000	8,000	8,000
Depreciation	0	0	0	0
Benefits, Losses and Expenses	33,000	11,000	61,000	21,000
Realized Investment Gains (Losses)	0	0	0	0
Managing General Agency Underwriter
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	13,000	10,000	31,000	25,000
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	1,000	1,000	5,000	4,000
Net Investment Income	0	0	0
Amortization of Intangible Assets	1,000	1,000	2,000	2,000
Total assets	155,000	137,000	155,000	137,000
Insurance Commissions and Fees	13,000	10,000	31,000	25,000
Other Cost and Expense, Operating	3,000	2,000	6,000	5,000
Insurance Commissions	8,000	6,000	18,000	14,000
Depreciation	0	0	0	0
Benefits, Losses and Expenses	12,000	9,000	26,000	20,000
Corporate and Other
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	6,000	2,000	8,000	4,000
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	(11,000)	(4,000)	(16,000)	(3,000)
Net Investment Income	2,000	2,000	4,000	4,000
Total assets	216,000	225,000	216,000	225,000
Derivative, Gain (Loss) on Derivative, Net	0	0	0	0
Other Cost and Expense, Operating	17,000	6,000	24,000	7,000
Depreciation	0	0	1,000	0
Benefits, Losses and Expenses	17,000	6,000	24,000	8,000
Realized Investment Gains (Losses)	5,000	0	5,000	0
Other income Items	0	0	0	0
Property and Casualty, Commercial Insurance
Segment Reporting, Revenue Reconciling Item [Line Items]
Contractually Specified Servicing Fee, Late Fee, and Ancillary Fee Earned in Exchange for Servicing Financial Asset	3,000	2,000	6,000	4,000
Other income Items	0	0	0	0
Deferred Policy Acquisition Costs, Amortization Expense	5,000	1,000	10,000	3,000
Insurance Distribution
Segment Reporting, Revenue Reconciling Item [Line Items]
Other income Items	$ 0	$ 0	$ 0	$ 0

Investments - Summary of Amorti

Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 1,159	$ 1,032
Debt Securities, Available-for-sale, Allowance for Credit Loss	3	3	$ 1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	45	40
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	372	187
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5	4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	787	844
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	71	68
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	78	71
Fixed maturity securities, at fair value	2,043
Debt Securities, Available-for-sale, Amortized Cost	2,078	2,197
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Period Increase (Decrease)	0
Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	46	4
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	46	4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Fixed maturity securities, at fair value	314	426
Debt Securities, Available-for-sale, Amortized Cost	314	426
Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	1,113	1,028
Debt Securities, Available-for-sale, Allowance for Credit Loss	3	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	45	40
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	326	184
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5	4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	787	844
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	71	68
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	77	71
Fixed maturity securities, at fair value	1,703	1,710
Debt Securities, Available-for-sale, Amortized Cost	1,737	1,744
Fixed Income Securities [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	35	23
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	21	7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	15	16
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2	1
Fixed maturity securities, at fair value	71	72
Debt Securities, Available-for-sale, Amortized Cost	71	72
Fixed Income Securities [Member] | Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	618	584
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2	4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	125	75
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3	2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	493	509
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	43	43
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	46	44
Fixed maturity securities, at fair value	742	745
Debt Securities, Available-for-sale, Amortized Cost	786	785
Fixed Income Securities [Member] | Foreign Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	80	64
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	25	8
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	55	56
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	7	6
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	7	6
Fixed maturity securities, at fair value	105	100
Debt Securities, Available-for-sale, Amortized Cost	111	105
Fixed Income Securities [Member] | US Government Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	95	63
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	58	27
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	37	37
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4	4
Fixed maturity securities, at fair value	105	82
Debt Securities, Available-for-sale, Amortized Cost	108	85
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	129	104
Debt Securities, Available-for-sale, Allowance for Credit Loss	3	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	28	28
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	16	6
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	113	98
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	13	14
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	13	14
Fixed maturity securities, at fair value	253	250
Debt Securities, Available-for-sale, Amortized Cost	240	239
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	22	95
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	18	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3	93
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	1
Fixed maturity securities, at fair value	141	139
Debt Securities, Available-for-sale, Amortized Cost	141	139
Fixed Income Securities [Member] | Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	117	92
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	12	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	45	57
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	72	35
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	5	1
Fixed maturity securities, at fair value	241	303
Debt Securities, Available-for-sale, Amortized Cost	234	301
Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Unrealized Loss Position	17	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	17	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Fixed maturity securities, at fair value	46
Debt Securities, Available-for-sale, Amortized Cost	46
Fixed Income Securities [Member] | Collateralized Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Fixed maturity securities, at fair value	46	19
Debt Securities, Available-for-sale, Amortized Cost	46	19
Fixed Income Investments And Other Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	3	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	45	40
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	77	71
Fixed maturity securities, at fair value	2,017	2,135
Debt Securities, Available-for-sale, Amortized Cost	2,051	2,170
Collateral Pledged [Member] | Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1	0
Fixed maturity securities, at fair value	25	27
Debt Securities, Available-for-sale, Amortized Cost	27	0
Collateral Pledged [Member] | Fixed Income Securities [Member] | Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Fixed maturity securities, at fair value	0	27
Debt Securities, Available-for-sale, Amortized Cost	0	27
Collateral Pledged [Member] | Fixed Income Securities [Member] | US Treasury and Government
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1	0
Fixed maturity securities, at fair value	25	0
Debt Securities, Available-for-sale, Amortized Cost	27	0
Asset Pledged as Collateral [Member] | Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Amortized Cost	$ 27	$ 27

Investments - Summary of Amor_2

Investments - Summary of Amortized Cost and Estimated Fair Value of Available-for-Sale Investments, Excluding VIE Investments Held by Successor Ambac, by Contractual Maturity (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 2,078	$ 2,197
Fixed maturity securities, at fair value	2,043
Amortized Cost, Due in one year or less	439
Amortized Cost, Due after one year through five years	543
Amortized Cost, Due after five years through ten years	304
Amortized Cost, Due after ten years	132
Amortized Cost, Total	1,418
Estimated Fair Value, Due in one year or less	437
Estimated Fair Value, Due after one year through five years	521
Estimated Fair Value, Due after five years through ten years	279
Estimated Fair Value, Due after ten years	124
Estimated Fair Value due, Total	1,361
Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,737	1,744
Fixed maturity securities, at fair value	1,703	1,710
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	240	239
Fixed maturity securities, at fair value	253	250
Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	46
Fixed maturity securities, at fair value	46
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	141	139
Fixed maturity securities, at fair value	141	139
Fixed Income Securities [Member] | Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	234	301
Fixed maturity securities, at fair value	$ 241	$ 303

Investments - Summary of Gross

Investments - Summary of Gross Unrealized Losses and Fair Values of Ambac's Available-for-Sale Investments (Details) $ in Millions	Jun. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 372	$ 187
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5	4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	787	844
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	71	68
Debt Securities, Available-for-sale, Unrealized Loss Position	1,159	1,032
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	78	71
DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss, including pledged securities	7
Debt Securities , Available for sale, Continuous Unrealized Loss Position,	398	187
Debt Securities, Available for sale, Unrealized Loss Position, Including Pledged Securities		1,032
Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	46	4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	46	4
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 0	0
Ambac Insured Securities | Parsed Fixed Income Securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions	5,000
Fixed Income Investments And Other Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 77	71
Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	326	184
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	5	4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	787	844
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	71	68
Debt Securities, Available-for-sale, Unrealized Loss Position	1,113	1,028
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	77	71
Fixed Income Securities [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	21	7
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	15	16
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1	1
Debt Securities, Available-for-sale, Unrealized Loss Position	35	23
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2	1
Fixed Income Securities [Member] | Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	125	75
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3	2
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	493	509
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	43	43
Debt Securities, Available-for-sale, Unrealized Loss Position	618	584
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 46	44
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions	733,000
Fixed Income Securities [Member] | Debt Security, Government, Non-US [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 25	8
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	55	56
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	7	6
Debt Securities, Available-for-sale, Unrealized Loss Position	80	64
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	7	6
Fixed Income Securities [Member] | US Government Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	58	27
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	37	37
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	3	2
Debt Securities, Available-for-sale, Unrealized Loss Position	95	63
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4	4
Fixed Income Securities [Member] | US Government Debt Securities [Member] | Asset Pledged as Collateral [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	25	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	25	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1	0
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	16	6
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	113	98
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	13	14
Debt Securities, Available-for-sale, Unrealized Loss Position	129	104
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	13	14
Fixed Income Securities [Member] | Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	17	3
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	17	3
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Fixed Income Securities [Member] | Collateralized Debt Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	18	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3	93
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	1
Debt Securities, Available-for-sale, Unrealized Loss Position	22	95
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	1
Fixed Income Securities [Member] | Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	45	57
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1	1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	72	35
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	4	1
Debt Securities, Available-for-sale, Unrealized Loss Position	117	92
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 5	1
Debt Securities Available for Sale Unrealized Loss Measured as a Percent of Amortized Cost	5%
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions	13,000
Fixed Income Securities [Member] | Ambac Insured Securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 13
Debt Securities Available for Sale Unrealized Loss Measured as a Percent of Amortized Cost	12%
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions	15,000
Collateral Pledged [Member] | Fixed Income Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 1	0
Collateral Pledged [Member] | Fixed Income Securities [Member] | Short-term Investments [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 0	$ 0

Investments - Additional Inform

Investments - Additional Information (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 3,000	$ 3,000	$ 1,000
Securities fair value	29,000	24,000
Debt Securities, Available-for-sale, Unrealized Loss Position	1,159,000	1,032,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	78,000	71,000
Debt Securities, Available for sale, Unrealized Loss Position, Accumulated Loss, Including Pledged Securities	$ 1,184,000
Average Percentage of Unrealized Loss Versus Amortized Cost for Below Investment Grade Securities	8%
Average Percentage of Unrealized Loss Versus Amortized Cost for Investment Grade Securities	7%
Fiduciary Funds Held by Insurance Distribution Subsidiaries	$ 2,000	2,000
Investment Portfolio [Member]
Schedule of Investments [Line Items]
Fair Value of Cash and Securities Pledged to Derivative Counterparties	25,000	27,000
Fixed Income Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	3,000	3,000
Debt Securities, Available-for-sale, Unrealized Loss Position	1,113,000	1,028,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	77,000	71,000
Fixed Income Securities [Member] | Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	618,000	584,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	46,000	44,000
Fixed Income Securities [Member] | Corporate Debt Securities [Member] | External Credit Rating, Investment Grade
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	45,000
Fixed Income Securities [Member] | Corporate Debt Securities [Member] | External Credit Rating, Non Investment Grade [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	483
Fixed Income Securities [Member] | Residential Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	3,000	3,000
Debt Securities, Available-for-sale, Unrealized Loss Position	129,000	104,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	13,000	14,000
Fixed Income Securities [Member] | Asset-backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	117,000	92,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	5,000	1,000
Reported Value Measurement [Member]
Schedule of Investments [Line Items]
Other investments	153,000	77,000
Reported Value Measurement [Member] | Interest Rate Contract [Member]
Schedule of Investments [Line Items]
Other investments	$ 89,000	$ 39,000

Investments - Summary of Amount

Investments - Summary of Amounts Included in Net Realized (Losses) Gains and Other-Than-Temporary Impairments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Investment [Line Items]
Foreign exchange (losses) gains			$ (1)	$ (3)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal)	$ (2)	$ 0	(1)	(1)
Debt Securities, Available-for-sale, Allowance for Credit Loss, Sell before Recovery	0	0	0	0
Realized Investment Gains (Losses)	4	(3)	4	(8)
Fair Value of Securities Deposited in Connection wtih Letter of Credit	1		1		$ 1
Debt Securities, Available-for-sale, Realized Gain	7	0	7	1
Debt Securities, Available-for-sale, Realized Loss	1	2	1	3
Available-for-sale Securities, Gross Realized Losses	(1)	(2)	(1)	(3)
Gain (Loss) on Investments [Member]
Investment [Line Items]
Foreign exchange (losses) gains	$ (1)	$ (2)	$ 0	$ (4)

Investments - Summary of Source

Investments - Summary of Sources of Collateral Received and Various Investment Agreement in which Collateral Pledged (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Investment [Line Items]
Fair Value Of Securities Deposited With Governmental Authorities	$ 29	$ 24
Fair Value of Securities Deposited in Connection wtih Letter of Credit	$ 1	1
Standard & Poor's, B Rating [Member]
Investment [Line Items]
Investment Owned, at Fair Value		482
Standard & Poor's, B Rating [Member] | Municipal Bonds [Member]
Investment [Line Items]
Investment Owned, at Fair Value		$ 9

Investments - Summary of Fair V

Investments - Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Standard & Poor's, B Rating [Member]
Schedule of Investments [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		$ 482
Standard & Poor's, B- Rating [Member]
Schedule of Investments [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	$ 403
Municipal Bonds [Member] | Standard & Poor's, B Rating [Member]
Schedule of Investments [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors		$ 9
Municipal Bonds [Member] | Standard & Poor's, B- Rating [Member]
Schedule of Investments [Line Items]
Fair value of securities that include benefit of guarantees provided by financial guarantors	$ 8

Investments - Summary of Fair_2

Investments - Summary of Fair Value, Including Financial Guarantee, and Weighted-Average Underlying Rating, Excluding Financial Guarantee, of Insured Securities (Phantom) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Investment [Line Items]
Investment expense	$ (1)	$ (1)	$ (3)	$ (3)
Net investment income	36	35	78	69
Standard & Poor's, B- Rating [Member]
Investment [Line Items]
Investment Owned, at Fair Value	403		403
Standard & Poor's, B- Rating [Member] | Mortgage-Backed Securities, Other
Investment [Line Items]
Investment Owned, at Fair Value	244		244
Standard & Poor's, B- Rating [Member] | Asset-backed Securities [Member]
Investment [Line Items]
Investment Owned, at Fair Value	151		151
Standard & Poor's, B Rating [Member]
Investment [Line Items]
Investment Owned, at Fair Value					$ 482
Standard & Poor's, B Rating [Member] | Mortgage-Backed Securities, Other
Investment [Line Items]
Investment Owned, at Fair Value					240
Standard & Poor's, B Rating [Member] | Asset-backed Securities [Member]
Investment [Line Items]
Investment Owned, at Fair Value					$ 232
Gains (losses) on securities held as of reporting date [Member]
Investment [Line Items]
Other Investments Income	2	2	9	6
Fixed Income Investments [Member]
Investment [Line Items]
Gross Investment Income, Operating	22	19	45	35
Short-Term [Member]
Investment [Line Items]
Gross Investment Income, Operating	5	5	10	10
Other Investments [Member]
Investment [Line Items]
Gross Investment Income, Operating	$ 8	$ 9	$ 21	$ 22

Investments - Summary of Net In

Investments - Summary of Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Investment [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)	$ 3	$ 6
Interest Income, Debt Securities, Available-for-Sale, Operating	26	22	$ 52	$ 43
Short-term Investments [Member]
Investment [Line Items]
Gross Investment Income, Operating	5	5	10	10
Fixed Income Investments [Member]
Investment [Line Items]
Gross Investment Income, Operating	22	19	45	35
Fixed Income Securities, Trading
Investment [Line Items]
Gross Investment Income, Operating	$ 2	$ 4	$ 4	$ 5

Investments Investments - Equit

Investments Investments - Equity Investments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Schedule of Equity Method Investments [Line Items]
Equity Securities Excluded From Fair Value Table	$ 26		$ 26		$ 13
Equity Securities, FV-NI, Realized Gain (Loss)	3	$ 6
Debt Securities, Available-for-sale, Allowance for Credit Loss	3	1	3	$ 1	3
Net Realized and Unrealized Gain (Loss) on Trading Securities		$ 9
Debt Securities, Trading, Realized Gain (Loss)	5
Other than Temporary Impairment Losses, Investments			1
Real Estate [Member]
Schedule of Equity Method Investments [Line Items]
Other investments					21
Hedge Funds, Multi-strategy [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	117		117		112
Illiquid Investments [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	83		83		84
Insurance Linked [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	0		0		1
Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	79		79		70
Equity investments in pooled funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	533		533		463
Convertibles and Bonds with Warrants Attached
Schedule of Equity Method Investments [Line Items]
Other investments	23		23		0
Fixed Income Funds
Schedule of Equity Method Investments [Line Items]
Other investments	53		53		52
Equity Funds
Schedule of Equity Method Investments [Line Items]
Other investments	40		40		38
Real Estate Funds
Schedule of Equity Method Investments [Line Items]
Other investments	0		0
High Yield Fund
Schedule of Equity Method Investments [Line Items]
Other investments	137		137		85
Priced Through Pricing Vendors [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	153		153		77
Priced Through Pricing Vendors [Member] | Interest Rate Contract [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	89		89		39
Priced Through Pricing Vendors [Member] | Equity [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	40		40		38
Priced Through Pricing Vendors [Member] | Convertibles and Bonds with Warrants Attached
Schedule of Equity Method Investments [Line Items]
Other investments	23		23		$ 0
Gains (losses) on securities held as of reporting date [Member]
Schedule of Equity Method Investments [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)			3	10
Net Realized and Unrealized Gain (Loss) on Trading Securities			12	$ 16
Commitments [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	$ 30		$ 30

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Carrying Amount and Fair Value of Ambac's Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	$ 2,043,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	3,000	$ 3,000	$ 1,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	45,000	40,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	78,000	71,000
Financial assets:
Derivative assets	18,000	26,000
Other assets	0
Long-term Debt	515,000	508,000
Financial liabilities:
Derivative liabilities	26,000	35,000
Equity Securities Excluded From Fair Value Table	26,000	13,000
Debt Securities, Available-for-sale, Amortized Cost	2,078,000	2,197,000
Debt Securities, Available-for-Sale, Current	2,043,000	2,162,000
Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	1,703,000	1,710,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	3,000	3,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	45,000	40,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	77,000	71,000
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	1,737,000	1,744,000
Fixed Income Investments And Other Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	2,017,000	2,135,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	3,000	3,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	45,000	40,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	77,000	71,000
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	2,051,000	2,170,000
Commercial Mortgage Backed Securities [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	46,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	46,000
Short-term Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	314,000	426,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	314,000	426,000
Asset-backed Securities [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	241,000	303,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	12,000	3,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	5,000	1,000
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	234,000	301,000
Collateralized Debt Obligations [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	141,000	139,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,000	1,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	1,000
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	141,000	139,000
Residential Mortgage-Backed Securities [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	253,000	250,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	3,000	3,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	28,000	28,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	13,000	14,000
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	240,000	239,000
US Government Debt Securities [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	105,000	82,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	1,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	4,000	4,000
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	108,000	85,000
Debt Security, Government, Non-US [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	105,000	100,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	1,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	7,000	6,000
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	111,000	105,000
Corporate Debt Securities [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	742,000	745,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	2,000	4,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	46,000	44,000
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	786,000	785,000
Municipal Bonds [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	71,000	72,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,000	1,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	2,000	1,000
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	71,000	72,000
Collateralized Mortgage Backed Securities [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	46,000	19,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	46,000	19,000
Total Fair Value [Member]
Financial assets:
Cash	35,000	28,000
Reported Value Measurement [Member]
Financial assets:
Other investments	153,000	77,000
Cash	35,000	28,000
Loans	2,000	2,000
Total financial assets	6,626,000	7,022,000
Financial liabilities:
Liabilities for net financial guarantees written	229,000	292,000
Long-term debt	1,015,000	983,000
Total financial liabilities	5,258,000	5,474,000
Reported Value Measurement [Member] | Short-term Investments [Member]
Financial assets:
Short term investments	314,000	426,000
Reported Value Measurement [Member] | Other Debt Obligations [Member]
Financial assets:
Other investments	558,000	475,000
Reported Value Measurement [Member] | Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities	25,000	35,000
Reported Value Measurement [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Financial assets:
Derivative assets	18,000	25,000
Reported Value Measurement [Member] | Warrants [Member]
Financial assets:
Derivative assets	1,000	1,000
Reported Value Measurement [Member] | Foreign Exchange Future
Financial liabilities:
Derivative liabilities	0	0
Level 1 [Member]
Financial assets:
Cash	35,000	27,000
Total financial assets	797,000	979,000
Financial liabilities:
Liabilities for net financial guarantees written	0	0
Long-term debt	0	0
Total financial liabilities	0	0
Level 1 [Member] | Short-term Investments [Member]
Financial assets:
Short term investments	313,000	421,000
Level 1 [Member] | Loans Receivable [Member]
Financial assets:
Loans	0	0
Level 1 [Member] | Other Debt Obligations [Member]
Financial assets:
Other investments	153,000	77,000
Level 1 [Member] | Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities	0	0
Level 1 [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Financial assets:
Derivative assets	0	0
Level 1 [Member] | Warrants [Member]
Financial assets:
Derivative assets	0	0
Level 1 [Member] | Foreign Exchange Future
Financial liabilities:
Derivative liabilities	0	0
Level 2 [Member]
Financial assets:
Cash	0	2,000
Total financial assets	1,748,000	1,795,000
Financial liabilities:
Liabilities for net financial guarantees written	0	0
Long-term debt	753,000	679,000
Total financial liabilities	4,561,000	4,671,000
Level 2 [Member] | Short-term Investments [Member]
Financial assets:
Short term investments	1,000	5,000
Level 2 [Member] | Loans Receivable [Member]
Financial assets:
Loans	0	0
Level 2 [Member] | Other Debt Obligations [Member]
Financial assets:
Other investments	0	0
Level 2 [Member] | Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities	25,000	35,000
Level 2 [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Financial assets:
Derivative assets	0	0
Level 2 [Member] | Warrants [Member]
Financial assets:
Derivative assets	0	0
Level 2 [Member] | Foreign Exchange Future
Financial liabilities:
Derivative liabilities	0	0
Level 3 [Member]
Financial assets:
Cash	0	0
Total financial assets	3,675,000	3,850,000
Financial liabilities:
Liabilities for net financial guarantees written	488,000	788,000
Long-term debt	19,000	18,000
Total financial liabilities	712,000	1,026,000
Level 3 [Member] | Short-term Investments [Member]
Financial assets:
Short term investments	0	0
Level 3 [Member] | Loans Receivable [Member]
Financial assets:
Loans	1,000	2,000
Level 3 [Member] | Other Debt Obligations [Member]
Financial assets:
Other investments	0	0
Level 3 [Member] | Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities	0	0
Level 3 [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Financial assets:
Derivative assets	18,000	25,000
Level 3 [Member] | Warrants [Member]
Financial assets:
Derivative assets	1,000	1,000
Level 3 [Member] | Foreign Exchange Future
Financial liabilities:
Derivative liabilities	0	0
Commercial Mortgage Backed Securities [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	46,000	19,000
Municipal Bonds [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	101,000	99,000
Corporate Debt Securities [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	742,000	745,000
Debt Security, Government, Non-US [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	105,000	100,000
US Government Debt Securities [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	105,000	82,000
Residential Mortgage-Backed Securities [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	253,000	250,000
Collateralized Debt Obligations [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	141,000	139,000
Asset-backed Securities [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	241,000	303,000
Fair Value, Recurring [Member]
Financial assets:
Total financial assets	6,600,000	7,010,000
Financial liabilities:
Liabilities for net financial guarantees written	488,000	788,000
Long-term debt	772,000	697,000
Total financial liabilities	5,273,000	5,697,000
Fair Value, Recurring [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	46,000	19,000
Fair Value, Recurring [Member] | Short-term Investments [Member]
Financial assets:
Short term investments	314,000	426,000
Fair Value, Recurring [Member] | Loans Receivable [Member]
Financial assets:
Loans	1,000	2,000
Fair Value, Recurring [Member] | Other Debt Obligations [Member]
Financial assets:
Other investments	533,000	463,000
Fair Value, Recurring [Member] | Asset-backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	241,000	303,000
Fair Value, Recurring [Member] | Collateralized Debt Obligations [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	141,000	139,000
Fair Value, Recurring [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	253,000	250,000
Fair Value, Recurring [Member] | US Government Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	105,000	82,000
Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	105,000	100,000
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	742,000	745,000
Fair Value, Recurring [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	101,000	99,000
Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Financial liabilities:
Derivative liabilities	25,000	35,000
Fair Value, Recurring [Member] | Interest Rate Swap [Member] | Other Assets [Member]
Financial assets:
Derivative assets	18,000	25,000
Fair Value, Recurring [Member] | Warrants [Member]
Financial assets:
Derivative assets	1,000	1,000
Fair Value, Recurring [Member] | Foreign Exchange Future
Financial liabilities:
Derivative liabilities	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Asset-backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Collateralized Debt Obligations [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | US Government Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	105,000	82,000
Fair Value, Recurring [Member] | Level 1 [Member] | Debt Security, Government, Non-US [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	105,000	100,000
Fair Value, Recurring [Member] | Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 1 [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 2 [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	46,000	19,000
Fair Value, Recurring [Member] | Level 2 [Member] | Asset-backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	164,000	235,000
Fair Value, Recurring [Member] | Level 2 [Member] | Collateralized Debt Obligations [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	141,000	139,000
Fair Value, Recurring [Member] | Level 2 [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	253,000	250,000
Fair Value, Recurring [Member] | Level 2 [Member] | US Government Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 2 [Member] | Debt Security, Government, Non-US [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	742,000	726,000
Fair Value, Recurring [Member] | Level 2 [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	101,000	99,000
Fair Value, Recurring [Member] | Level 3 [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Asset-backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	77,000	68,000
Fair Value, Recurring [Member] | Level 3 [Member] | Collateralized Debt Obligations [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Residential Mortgage-Backed Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | US Government Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Debt Security, Government, Non-US [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Fair Value, Recurring [Member] | Level 3 [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	19,000
Fair Value, Recurring [Member] | Level 3 [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Collateral Pledged [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	25,000	27,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,000	0
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	27,000	0
Collateral Pledged [Member] | Short-term Investments [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	27,000
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	0	27,000
Collateral Pledged [Member] | US Government Debt Securities [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	25,000	0
Collateral Pledged [Member] | Short-term Investments [Member] | Reported Value Measurement [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	27,000
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Short-term Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	27,000
Collateral Pledged [Member] | Fair Value, Recurring [Member] | US Government Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	25,000	0
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 1 [Member] | Short-term Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	27,000
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 1 [Member] | US Government Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	25,000	0
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 2 [Member] | Short-term Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 2 [Member] | US Government Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 3 [Member] | Short-term Investments [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Collateral Pledged [Member] | Fair Value, Recurring [Member] | Level 3 [Member] | US Government Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Asset Pledged as Collateral [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	27,000	27,000
Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	2,101,000	2,167,000
Financial assets:
Loans	1,567,000	1,663,000
Derivative assets	208,000	226,000
Long-term Debt	2,853,000	2,967,000
Financial liabilities:
Derivative liabilities	1,136,000	1,197,000
Long-term debt	2,599,000	2,710,000
Variable Interest Entity, Primary Beneficiary [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	2,010,000	2,072,000
Variable Interest Entity, Primary Beneficiary [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	91,000	95,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	6,000	7,000
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Financial liabilities:
Debt Securities, Available-for-sale, Amortized Cost	85,000	88,000
Variable Interest Entity, Primary Beneficiary [Member] | Reported Value Measurement [Member]
Financial assets:
Restricted Cash and Cash Equivalents, Current	62,000	246,000
Loans	1,567,000	1,663,000
Financial liabilities:
Long-term debt	2,853,000	2,967,000
Variable Interest Entity, Primary Beneficiary [Member] | Reported Value Measurement [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	2,010,000	2,072,000
Variable Interest Entity, Primary Beneficiary [Member] | Reported Value Measurement [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	91,000		$ 95,000
Variable Interest Entity, Primary Beneficiary [Member] | Reported Value Measurement [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative assets	174,000	190,000
Financial liabilities:
Derivative liabilities	1,136,000	1,197,000
Variable Interest Entity, Primary Beneficiary [Member] | Reported Value Measurement [Member] | Currency Swaps [Member]
Financial assets:
Derivative assets	34,000	36,000
Variable Interest Entity, Primary Beneficiary [Member] | Level 1 [Member]
Financial assets:
Restricted Cash and Cash Equivalents, Current	62,000	246,000
Loans	0	0
Financial liabilities:
Long-term debt	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Level 1 [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Level 1 [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative assets	0	0
Financial liabilities:
Derivative liabilities	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Level 1 [Member] | Currency Swaps [Member]
Financial assets:
Derivative assets	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Level 2 [Member]
Financial assets:
Restricted Cash and Cash Equivalents, Current	0
Loans	0	0
Financial liabilities:
Long-term debt	2,646,000	2,760,000
Variable Interest Entity, Primary Beneficiary [Member] | Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Level 2 [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	91,000	95,000
Variable Interest Entity, Primary Beneficiary [Member] | Level 2 [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative assets	174,000	190,000
Financial liabilities:
Derivative liabilities	1,136,000	1,197,000
Variable Interest Entity, Primary Beneficiary [Member] | Level 2 [Member] | Currency Swaps [Member]
Financial assets:
Derivative assets	34,000	36,000
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member]
Financial assets:
Restricted Cash and Cash Equivalents, Current	0	0
Loans	1,567,000	1,663,000
Financial liabilities:
Long-term debt	205,000	220,000
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	2,010,000	2,072,000
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative assets	0	0
Financial liabilities:
Derivative liabilities	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Level 3 [Member] | Currency Swaps [Member]
Financial assets:
Derivative assets	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Recurring [Member]
Financial assets:
Restricted Cash and Cash Equivalents, Current	62,000	246,000
Loans	1,567,000	1,663,000
Financial liabilities:
Long-term debt	2,852,000	2,980,000
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	2,010,000	2,072,000
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Recurring [Member] | Municipal Bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Fixed maturity securities, at fair value	91,000	95,000
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Financial assets:
Derivative assets	174,000	190,000
Financial liabilities:
Derivative liabilities	1,136,000	1,197,000
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Recurring [Member] | Currency Swaps [Member]
Financial assets:
Derivative assets	$ 34,000	$ 36,000

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Derivative liabilities	$ 26	$ 35
Weighted average discounted rate of estimated future premium payments to be paid by the VIEs	3.20%	3.20%
Derivative assets	$ 18	$ 26
Derivative assets	18	26
Warrants [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Derivative assets	1	1
Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Other investments	$ 380	$ 386
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	2%	2%
Minimum [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Percentage of investment portfolio valued using internal valuation models	4%	4%
Maximum [Member] | Fixed Income Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Percentage of investment portfolio valued using external pricing services	94%	94%
Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Derivative liabilities	$ 1,136	$ 1,197
Weighted average discounted rate of estimated future premium payments to be paid by the VIEs	6.60%	6.30%
Derivative assets	$ 208	$ 226
Derivative assets	$ 208	$ 226

Fair Value Measurements - Infor

Fair Value Measurements - Information about Valuation Inputs for Fixed Income Securities Classified as Level 3 (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Inputs Yield Rate						11.20%
Asset-backed Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Coupon rate	5.98%			5.98%		5.97%
Fair Value Inputs Maturity		12 years 9 months 18 days		12 years 5 months 19 days
Yield	10%			10%		12%
Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	$ 3,672,000	$ 3,782,000	$ 3,831,000	$ 3,672,000	$ 3,831,000	$ 3,848,000	$ 3,972,000	$ 3,762,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(106,000)		(81,000)	(170,000)	(155,000)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held				16,000	73,000
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss)	(19,000)		(124,000)
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	15,000		64,000	(23,000)	152,000
Fair Value, Inputs, Level 3 [Member] | Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	77,000	$ 87,000	81,000	77,000	81,000	87,000	81,000	79,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(26,000)		0	(27,000)	(1,000)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held				7,000	1,000
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss)	7,000
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	9,000			9,000	3,000
Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	18,000		25,000	18,000	25,000	26,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements				0
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held				(8,000)
Corporate Obligations [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Inputs Maturity		10 months 20 days
Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability								26,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements					0
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held					0
Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	18,000	$ 21,000	25,000	18,000	25,000		31,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	0		0
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss)	(3,000)		(5,000)
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	0		0	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Obligations [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability								1,828,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements					(12,000)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held					80,000
Variable Interest Entity, Primary Beneficiary [Member] | Fair Value, Inputs, Level 3 [Member] | Loans Receivable [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability								$ 1,829,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements					(141,000)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held					(7,000)
Variable Interest Entity, Primary Beneficiary [Member] | Investment Contracts [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	2,010,000		1,952,000	2,010,000	1,952,000	2,072,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements				(12,000)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held				(32,000)
Variable Interest Entity, Primary Beneficiary [Member] | Investment Contracts [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Obligations [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	2,010,000	2,070,000	1,952,000	2,010,000	1,952,000		2,003,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(12,000)		(12,000)
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss)	(51,000)		(53,000)
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	3,000		14,000	(18,000)	57,000
Variable Interest Entity, Primary Beneficiary [Member] | Loan Origination Commitments [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	1,567,000		1,772,000	1,567,000	1,772,000	$ 1,663,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements				(132,000)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held				49,000
Variable Interest Entity, Primary Beneficiary [Member] | Loan Origination Commitments [Member] | Fair Value, Inputs, Level 3 [Member] | Loans Receivable [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	1,567,000	$ 1,604,000	1,772,000	1,567,000	1,772,000		$ 1,856,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(68,000)		(69,000)
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss)	29,000		(66,000)
Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), OCI	$ 3,000		$ 50,000	$ (14,000)	$ 92,000

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Information about Described Model Inputs Used to Determine Fair Value of Each Class of Credit Derivatives (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value of derivative liabilities		$ 25
Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair value of derivative liabilities		0
Real Estate [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other investments			$ 21
Illiquid Investments [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Other investments		$ 83	$ 84
Asset-backed Securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Inputs Coupon Rate		5.98%	5.97%
Fair Value Inputs Maturity	12 years 9 months 18 days	12 years 5 months 19 days
Fair Value Inputs Yield		10%	12%

Fair Value Measurements - Inf_2

Fair Value Measurements - Information about Valuation Inputs for Variable Interest Entity Assets and Liabilities Classified as Level 3 (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Estimated Future Premium Payments Minimum Discounted Rate	5.80%		5.80%		5.30%
Estimated Future Premium Payments Maximum Discounted Rate	8.20%		8.20%		7.80%
Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	$ 3,672,000	$ 3,831,000	$ 3,672,000	$ 3,831,000		$ 3,782,000	$ 3,848,000	$ 3,972,000	$ 3,762,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings	(19,000)	(124,000)	16,000	73,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	15,000	64,000	(23,000)	152,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(106,000)	(81,000)	(170,000)	(155,000)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			16,000	73,000
Fair Value, Inputs, Level 3 [Member] | Investments [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	77,000	81,000	77,000	81,000		87,000	87,000	81,000	79,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings	7,000	0	7,000	1,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	9,000	0	9,000	3,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(26,000)	0	(27,000)	(1,000)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			7,000	1,000
Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	18,000	25,000	18,000	25,000			26,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings			(8,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss			0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements			0
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			(8,000)
Fair Value, Inputs, Level 3 [Member] | Loans Receivable [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability									1,829,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings				(7,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss				92,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements				(141,000)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held				(7,000)
Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability									1,828,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings				80,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss				57,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements				(12,000)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held				80,000
Loan Origination Commitments [Member] | Fair Value, Inputs, Level 3 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	1,567,000	1,772,000	1,567,000	1,772,000			1,663,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings			49,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss			(14,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements			(132,000)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			49,000
Loan Origination Commitments [Member] | Fair Value, Inputs, Level 3 [Member] | Loans Receivable [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	1,567,000	1,772,000	1,567,000	1,772,000		1,604,000		1,856,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings	29,000	(66,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	3,000	50,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(68,000)	(69,000)
Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability									$ 26,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings				0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss				0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements				0
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held				0
Derivative Financial Instruments, Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	18,000	25,000	18,000	25,000		21,000		31,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings	(3,000)	(5,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	0	0
Investment Contracts [Member] | Fair Value, Inputs, Level 3 [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	2,010,000	1,952,000	2,010,000	1,952,000			$ 2,072,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings			(32,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss			(18,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements			(12,000)
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			(32,000)
Investment Contracts [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value Inputs, Liabilities, Quantitative Information [Line Items] (Deprecated 2018-01-31)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability	2,010,000	1,952,000	$ 2,010,000	$ 1,952,000		$ 2,070,000		$ 2,003,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Earnings	(51,000)	(53,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Gain Loss Included In Other Comprehensive Income Loss	3,000	14,000
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	$ (12,000)	$ (12,000)

Fair Value Measurements - Sum_3

Fair Value Measurements - Summary of Changes in Level 3 Fair Value Category (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) level3FinancialInstruments	Jun. 30, 2023 USD ($) level3FinancialInstruments
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis Asset or Liability, Transfers into or out of Level 3 | level3FinancialInstruments			0	0
Level 3 [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	$ (106,000)	$ (81,000)	$ (170,000)	$ (155,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases			0	0
Level 3 [Member] | Investment Contracts [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements			(12,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases			0
Level 3 [Member] | Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements			(132,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases			0
Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements				0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases				0
Level 3 [Member] | Loans Receivable [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements				(141,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases				0
Level 3 [Member] | Loans Receivable [Member] | Loans [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(68,000)	(69,000)
Level 3 [Member] | Investments [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	(26,000)	0	(27,000)	(1,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases			0	0
Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements			0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases			$ 0
Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	0	0
Level 3 [Member] | Corporate Debt Securities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements				(12,000)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Purchases				$ 0
Level 3 [Member] | Corporate Debt Securities [Member] | Investment Contracts [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Or Liability Settlements	$ (12,000)	$ (12,000)

Fair Value Measurements - Sum_4

Fair Value Measurements - Summary of Gains and Losses (Realized and Unrealized) Relating to Level 3 Assets and Liabilities Included in Earnings (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2022
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	$ 7	$ 0	$ 7	$ 1
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	9	0	9		$ 0
Interest Rate Swap [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held			(8)		0
Gain (Loss) on Derivative Instruments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	(3)	(5)	(8)	$ 0
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	(3)	(5)
Income Loss On Variable Interest Entities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Total gains or losses included in earnings for the period	(22)	(119)	17		72
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	(22)	(119)	17		72
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	0	0	0		0
Fair Value Asset Or Liability Measured On Recurring Basis Change In Unrealized Gains Losses Still Held	$ 0	$ 0	$ 0		$ 0

Insurance Contracts - Additiona

Insurance Contracts - Additional Information (Details) $ in Thousands, € in Millions, £ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 GBP (£)	Jun. 30, 2024 EUR (€)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jun. 30, 2023 GBP (£)	Jun. 30, 2023 EUR (€)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Insurance [Line Items]
Reinsurance Recoverable Credit Exposure	$ 176,000		$ 176,000					$ 128,000
Estimated Future Premium Payments Weighted Average Discounted Rate	3.20%		3.20%		3.20%	3.20%		3.20%
Reinsurance Payable	$ 140,000		$ 140,000					$ 90,000
Weighted average period of future premiums			7 years 7 months 6 days	8 years
Uncollectable premium receivables	3,000		$ 3,000					4,000
Reinsurance recoveries of losses included in losses and loss expenses			(98,000)	$ (45,000)
Amortization of Intangible Assets	8,000	$ 7,000	21,000	13,000
Intangible assets, less accumulated amortization	285,000		285,000					307,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,419,000	1,303,000	1,419,000	1,303,000			$ 1,418,000	$ 1,415,000			$ 1,307,000	$ 1,305,000
Past Due Premiums	1,000	0	$ 1,000	$ 0
Loss Reserves [Member]
Insurance [Line Items]
Weighted average risk-free rate used to discount loss reserves			4.40%	4.60%
United Kingdom, Pounds
Insurance [Line Items]
Financial Guarantee Insurance Contracts, Premium Receivable	70,000	76,000	$ 70,000	$ 76,000	£ 55				£ 60
Euro Member Countries, Euro
Insurance [Line Items]
Financial Guarantee Insurance Contracts, Premium Receivable	$ 12,000	$ 14,000	$ 12,000	$ 14,000		€ 11				€ 12

Financial Guarantee Insurance C

Financial Guarantee Insurance Contracts - Summary of Gross Premium Receivable Roll-Forward (Direct and Assumed Contracts) (Details) $ in Thousands, € in Millions, £ in Millions	3 Months Ended						6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2024 GBP (£)	Jun. 30, 2024 EUR (€)	Jun. 30, 2023 USD ($)	Jun. 30, 2023 GBP (£)	Jun. 30, 2023 EUR (€)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Insurance [Line Items]
Allowance for Doubtful Accounts, Premiums and Other Receivables	$ 3,000			$ 5,000			$ 3,000	$ 5,000	$ 3,000	$ 4,000	$ 5,000	$ 5,000
Past Due Premiums Receivable	0						0			0
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Uncollectable premiums							1,000	1,000
Other adjustments (including foreign exchange)							(1,000)	4,000
Premium Receivable, Allowance for Credit Loss	3,000						3,000			4,000
Premium Receivable, Credit Loss Expense (Reversal)	0			(1,000)			(2,000)	(1,000)
Premium Receivable, Allowance for Credit Loss, Writeoff	0			0			0	0
Premium Receivable, Allowance for Credit Loss, Recovery	0			0			0	0
Financing Receivable, 90 Days or More Past Due, Still Accruing	0						0			0
Premiums Receivable, Gross	317,000			276,000			317,000	276,000		290,000		269,000
Premiums Written, Gross							159,000
Proceeds from Insurance Premiums Collected							(134,000)	(90,000)
Adjustments for changes in expected and contractual cash flows							(2,000)	6,000
Accretion of premium receivable discount							4,000	4,000
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,419,000			1,303,000			1,419,000	1,303,000	$ 1,418,000	1,415,000	$ 1,307,000	$ 1,305,000
Premiums Receivable, Net	317,000						317,000			290,000
Fair Value, Recurring [Member] | Loans Receivable [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Written, Gross								83,000
Loans	1,000						1,000			2,000
Reported Value Measurement [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Other investments	153,000						153,000			77,000
Loans	2,000						2,000			2,000
Real Estate [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Other investments										21,000
Real Estate [Member] | Foreign Exchange
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Other adjustments (including foreign exchange)							(1,000)	4,000
Specialty Property & Casualty Program
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	85,000						85,000			46,000
Financial Guarantee
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	235,000						235,000			248,000
Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	135,000						135,000			140,000
Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	17,000						17,000			22,000
International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	82,000						82,000			85,000
I/SL [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	209,000						209,000			210,000
I/SL [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	128,000						128,000			133,000
I/SL [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3,000						3,000			4,000
I/SL [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	77,000						77,000			72,000
IA [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	8,000						8,000			16,000
IA [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3,000						3,000			3,000
IA [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
IA [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	5,000						5,000			13,000
II [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	5,000						5,000			5,000
II [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	5,000						5,000			5,000
II [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
II [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
III [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3,000						3,000			7,000
III [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
III [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3,000						3,000			7,000
III [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
IV [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	10,000						10,000			11,000
IV [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
IV [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	10,000						10,000			11,000
IV [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
United Kingdom, Pounds
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Ending premium receivable	70,000	£ 55		76,000	£ 60		70,000	76,000
Euro Member Countries, Euro
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Ending premium receivable	12,000		€ 11	$ 14,000		€ 12	12,000	$ 14,000
Other Public Finance Sectors [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	1,000						1,000			1,000
Other Public Finance Sectors [Member] | I/SL [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	1,000						1,000			1,000
Other Public Finance Sectors [Member] | IA [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Other Public Finance Sectors [Member] | II [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Other Public Finance Sectors [Member] | III [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Other Public Finance Sectors [Member] | IV [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Other International [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3,000						3,000			3,000
Other International [Member] | I/SL [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3,000						3,000			3,000
Other International [Member] | IA [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Other International [Member] | II [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Other International [Member] | III [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Other International [Member] | IV [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Mortgage Backed And Home Equity [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	11,000						11,000			12,000
Mortgage Backed And Home Equity [Member] | I/SL [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Mortgage Backed And Home Equity [Member] | IA [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Mortgage Backed And Home Equity [Member] | II [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Mortgage Backed And Home Equity [Member] | III [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Mortgage Backed And Home Equity [Member] | IV [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	10,000						10,000			11,000
Student Loans [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	4,000						4,000			7,000
Student Loans [Member] | I/SL [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Student Loans [Member] | IA [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Student Loans [Member] | II [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Student Loans [Member] | III [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3,000						3,000			7,000
Student Loans [Member] | IV [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	1,000						1,000			0
Other Structured Finance [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3,000						3,000			4,000
Other Structured Finance [Member] | I/SL [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3,000						3,000			4,000
Other Structured Finance [Member] | IA [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Other Structured Finance [Member] | II [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Other Structured Finance [Member] | III [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Other Structured Finance [Member] | IV [Member] | Structured Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Sovereign And Sub Sovereign [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	63,000						63,000			64,000
Sovereign And Sub Sovereign [Member] | I/SL [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	58,000						58,000			51,000
Sovereign And Sub Sovereign [Member] | IA [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	5,000						5,000			13,000
Sovereign And Sub Sovereign [Member] | II [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Sovereign And Sub Sovereign [Member] | III [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Sovereign And Sub Sovereign [Member] | IV [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Investor Owned And Public Utilities [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	16,000						16,000			18,000
Investor Owned And Public Utilities [Member] | I/SL [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	16,000						16,000			18,000
Investor Owned And Public Utilities [Member] | IA [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Investor Owned And Public Utilities [Member] | II [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Investor Owned And Public Utilities [Member] | III [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Investor Owned And Public Utilities [Member] | IV [Member] | International Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Housing Revenue [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	134,000						134,000			139,000
Housing Revenue [Member] | I/SL [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	127,000						127,000			131,000
Housing Revenue [Member] | IA [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	3,000						3,000			3,000
Housing Revenue [Member] | II [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	5,000						5,000			5,000
Housing Revenue [Member] | III [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	0						0			0
Housing Revenue [Member] | IV [Member] | Public Finance [Member]
Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward]
Premiums Receivable, Gross	$ 0						$ 0			$ 0

Insurance Contracts - Effect of

Insurance Contracts - Effect of Reinsurance on Premiums Written and Earned (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Direct Premiums Written	$ 93	$ 55	$ 174	$ 115
Assumed Reinsurance Premiums Written	20	0	38	0
Ceded Reinsurance Premiums Written	79	100	150	142
Premiums written, net of reinsurance	(34)	45	(62)	27
Direct Premiums Earned	79	52	154	98
Assumed Reinsurance Premiums Earned	17	0	33	0
Ceded Reinsurance Premiums Earned	$ 64	$ 37	$ 121	$ 69

Insurance Contracts - Summarize

Insurance Contracts - Summarized Future Gross Undiscounted Premiums Expected to be Collected, and Future Expected Premiums Earned, Net of Reinsurance (Details) $ in Millions	Jun. 30, 2024 USD ($)
Future premiums expected to be collected, September 30, 2021	$ 7
Future premiums expected to be collected, December 31, 2021	5
Future premiums expected to be collected, December 31, 2022	25
Future premiums expected to be collected, December 31, 2023	24
Future premiums expected to be collected, December 31, 2024	23
Future premiums expected to be collected, December 31, 2025	22
Future premiums expected to be collected, December 31, 2030	92
Future premiums expected to be collected, December 31, 2035	54
Future premiums expected to be collected, December 31, 2040	25
Future premiums expected to be collected, December 31, 2045	12
Future premiums expected to be collected, December 31, 2050	2
Future premiums expected to be collected, December 31, 2055	0
Future premiums expected to be collected, Total	293
Future expected premiums to be earned, net of reinsurance, September 30, 2021	4
Future expected premiums to be earned, net of reinsurance, December 31, 2021	4
Future expected premiums to be earned, net of reinsurance, December 31, 2022	15
Future expected premiums to be earned, net of reinsurance, December 31, 2023	15
Future expected premiums to be earned, net of reinsurance, December 31, 2024	15
Future expected premiums to be earned, net of reinsurance, December 31, 2025	14
Future expected premiums to be earned, net of reinsurance, December 31, 2030	54
Future expected premiums to be earned, net of reinsurance, December 31, 2035	27
Future expected premiums to be earned, net of reinsurance, December 31, 2040	9
Future expected premiums to be earned, net of reinsurance, December 31, 2045	4
Future expected premiums to be earned, net of reinsurance, December 31, 2050	1
Future expected premiums to be earned, net of reinsurance, December 31, 2055	0
Future expected premiums to be earned, net of reinsurance, Total	$ 163

Insurance Contracts Financial G

Insurance Contracts Financial Guarantee Insurance Contracts - Components of Loss and Loss Expense Reserves and Subrogation Recoverable (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered		$ 5
Policyholder Benefits and Claims Incurred, Ceded	$ 98	45
Subrogation recoverable	(128)		$ (137)
Claim liability reported on Balance Sheet, before reinsurance	476		559
Liability for Claims and Claims Adjustment Expense	890		893
Liability for Claim and Claim Adjustment Expenses Net of Subrogation recoverables	762	$ 724	756	$ 534
Property and Casualty, Commercial Insurance
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Liability for Claims and Claims Adjustment Expense	286		197
Liability for Claim and Claim Adjustment Expenses Net of Subrogation recoverables	286		197
Present Value of Expected Net Cash Flows- Claims and Loss Expenses [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Subrogation recoverable	7		1
Claim liability reported on Balance Sheet, before reinsurance	676		780
Liability for Claims and Claims Adjustment Expense	669		779
Present Value of Expected Net Cash Flows-Recoveries [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Subrogation recoverable	(136)		(139)
Claim liability reported on Balance Sheet, before reinsurance	(186)		(194)
Liability for Claims and Claims Adjustment Expense	(51)		(55)
Unearned Premium Reserve [Member]
Components of Loss and Loss Expense Reserves and Subrogation Recoverable [Line Items]
Subrogation recoverable	0		0
Claim liability reported on Balance Sheet, before reinsurance	(14)		(28)
Liability for Claims and Claims Adjustment Expense	$ (14)		$ (28)

Insurance Contracts - Summary o

Insurance Contracts - Summary of Loss Reserve Roll-Forward, Net of Subrogation Recoverable and Reinsurance (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Beginning balance of net loss and loss expense reserves	$ 570	$ 419
Current Year Claims and Claims Adjustment Expense	40	8
Prior Year Claims and Claims Adjustment Expense	(23)	18
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	17	25
Claim and loss expense payments, net of subrogation and reinsurance	(3)	(1)
Claim and loss expense (payments) recoveries, net of subrogation and reinsurance	(63)	136
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	66	(135)
Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss)	0	0
Liability for Unpaid Claims and Claims Adjustment Expense, Net	520	580	$ 570	$ 419
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	242	144	186	115
Policyholder Benefits and Claims Incurred, Ceded	98	45
Ceded Loss And Loss Expenses Paid Not Yet Recovered		5
Liability for Claim and Claim Adjustment Expenses Net of Subrogation recoverables	762	$ 724	756	$ 534
Financial Guarantee
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Ceded Loss And Loss Expenses Paid Not Yet Recovered	0		(1)
Loss Reserves Ceded To Reinsurers	$ 26		$ 30

Insurance Contracts - Summary_2

Insurance Contracts - Summary of Information Related to Policies Currently Included in Ambac's Loss Reserves or Subrogation Recoverable (Details) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2024	Jun. 30, 2024 USD ($) Policies	Dec. 31, 2023 USD ($) Policies	Jun. 30, 2023 USD ($)
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered				$ 5
Number of policies | Policies		143	141
Remaining weighted-average contract period (in years)	12 years	11 years
Gross insured contractual payments outstanding:
Principal		$ 2,581	$ 3,838
Interest		1,141	1,421
Total		3,722	5,259
Gross undiscounted claim liability		1,126	1,202
Discount, gross claim liability		452	426
Gross claim liability before all subrogation and before reinsurance		(674)	777
Less:
Gross other subrogation		(263)	(263)
Discount, other subrogation		77	69
Discounted other subrogation, before reinsurance		(186)	(194)
Gross claim liability, net of all subrogation and discounts, before reinsurance		(487)	583
Less: Unearned premium reserves		(14)	(28)
Plus: Loss adjustment expenses reserves		3	4
Claim liability reported on Balance Sheet, before reinsurance		476	559
Reinsurance recoverable reported on Balance Sheet		26	30
Financial Guarantee
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered		35
Financial Guarantee
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Loss Reserves Ceded To Reinsurers		26	30
Ceded Loss And Loss Expenses Paid Not Yet Recovered		$ 0	$ (1)
I/SL [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies		24	18
Remaining weighted-average contract period (in years)	9 years	5 years
Gross insured contractual payments outstanding:
Principal		$ 219	$ 429
Interest		18	75
Total		237	505
Gross undiscounted claim liability		0	1
Discount, gross claim liability		0	0
Gross claim liability before all subrogation and before reinsurance		0	1
Less:
Gross other subrogation		(13)	(13)
Discount, other subrogation		2	2
Discounted other subrogation, before reinsurance		(10)	(11)
Gross claim liability, net of all subrogation and discounts, before reinsurance		10	10
Less: Unearned premium reserves		0	0
Plus: Loss adjustment expenses reserves		1	0
Claim liability reported on Balance Sheet, before reinsurance		(9)	(10)
Reinsurance recoverable reported on Balance Sheet		$ 0	$ 1
IA [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies		3	8
Remaining weighted-average contract period (in years)	9 years	18 years
Gross insured contractual payments outstanding:
Principal		$ 194	$ 1,084
Interest		182	328
Total		376	1,412
Gross undiscounted claim liability		9	19
Discount, gross claim liability		2	2
Gross claim liability before all subrogation and before reinsurance		(7)	17
Less:
Gross other subrogation		(3)	(2)
Discount, other subrogation		0	0
Discounted other subrogation, before reinsurance		(3)	(2)
Gross claim liability, net of all subrogation and discounts, before reinsurance		(4)	(15)
Less: Unearned premium reserves		(2)	(12)
Plus: Loss adjustment expenses reserves		1	3
Claim liability reported on Balance Sheet, before reinsurance		2	6
Reinsurance recoverable reported on Balance Sheet		$ 0	$ 0
II [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies		10	9
Remaining weighted-average contract period (in years)	13 years	12 years
Gross insured contractual payments outstanding:
Principal		$ 439	$ 430
Interest		253	262
Total		692	692
Gross undiscounted claim liability		39	41
Discount, gross claim liability		7	7
Gross claim liability before all subrogation and before reinsurance		(32)	34
Less:
Gross other subrogation		(1)	0
Discount, other subrogation		0	0
Discounted other subrogation, before reinsurance		0	0
Gross claim liability, net of all subrogation and discounts, before reinsurance		(32)	34
Less: Unearned premium reserves		(4)	(4)
Plus: Loss adjustment expenses reserves		0	0
Claim liability reported on Balance Sheet, before reinsurance		28	30
Reinsurance recoverable reported on Balance Sheet		$ 8	$ 8
III [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies		11	13
Remaining weighted-average contract period (in years)	13 years	11 years
Gross insured contractual payments outstanding:
Principal		$ 269	$ 394
Interest		99	139
Total		368	534
Gross undiscounted claim liability		231	324
Discount, gross claim liability		77	86
Gross claim liability before all subrogation and before reinsurance		(155)	239
Less:
Gross other subrogation		(25)	(27)
Discount, other subrogation		4	4
Discounted other subrogation, before reinsurance		(21)	(23)
Gross claim liability, net of all subrogation and discounts, before reinsurance		(134)	215
Less: Unearned premium reserves		2	0
Plus: Loss adjustment expenses reserves		0	0
Claim liability reported on Balance Sheet, before reinsurance		136	215
Reinsurance recoverable reported on Balance Sheet		$ 14	$ 18
IV [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies		91	88
Remaining weighted-average contract period (in years)	12 years	12 years
Gross insured contractual payments outstanding:
Principal		$ 1,439	$ 1,473
Interest		573	600
Total		2,012	2,073
Gross undiscounted claim liability		809	772
Discount, gross claim liability		359	323
Gross claim liability before all subrogation and before reinsurance		(450)	450
Less:
Gross other subrogation		(211)	(208)
Discount, other subrogation		67	60
Discounted other subrogation, before reinsurance		(144)	(149)
Gross claim liability, net of all subrogation and discounts, before reinsurance		(307)	301
Less: Unearned premium reserves		(9)	(10)
Plus: Loss adjustment expenses reserves		1	1
Claim liability reported on Balance Sheet, before reinsurance		298	292
Reinsurance recoverable reported on Balance Sheet		$ 4	$ 3
V [Member]
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Number of policies | Policies		4	5
Remaining weighted-average contract period (in years)	7 years	8 years
Gross insured contractual payments outstanding:
Principal		$ 21	$ 27
Interest		16	17
Total		37	44
Gross undiscounted claim liability		37	44
Discount, gross claim liability		8	8
Gross claim liability before all subrogation and before reinsurance		(29)	36
Less:
Gross other subrogation		(11)	(11)
Discount, other subrogation		3	3
Discounted other subrogation, before reinsurance		(8)	(8)
Gross claim liability, net of all subrogation and discounts, before reinsurance		(21)	28
Less: Unearned premium reserves		(1)	(1)
Plus: Loss adjustment expenses reserves		0	0
Claim liability reported on Balance Sheet, before reinsurance		21	27
Reinsurance recoverable reported on Balance Sheet		$ 0	$ 0

Insurance Contracts - Summary_3

Insurance Contracts - Summary of Information Related to Policies Currently Included in Ambac's Loss Reserves or Subrogation Recoverable (Phantom) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Schedule of Insured Financial Obligations with Credit Deterioration [Line Items]
Subrogation recoverable	$ (128)	$ (137)
Liability for Claims	$ 890	$ 893
Ceded Loss And Loss Expenses Paid Not Yet Recovered			$ 5

Insurance Contracts Financial_2

Insurance Contracts Financial Guarantee Insurance Contracts - Summary of Percentage Ceded to Reinsurers and Reinsurance Recoverable and Rating Levels (Details) $ in Millions	Jun. 30, 2023 USD ($)
Insurance [Abstract]
Ceded Loss And Loss Expenses Paid Not Yet Recovered	$ 5

Insurance - Summary of Percenta

Insurance - Summary of Percentage Ceded to Reinsurers and Reinsurance Recoverable and Rating Levels (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Summary of Ceded Par and Net Unsecured Reinsurance Recoverable [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered			$ 5,000
Reinsurance Recoverable, Allowance for Credit Loss	$ 106	$ 75
Reinsurance Recoverables, Gross	277,000
Unsecured Reinsurance Recoverables	176,000
Reinsurance Recoverable, Gross, All Other	94,000
Unsecured Reinsurance Recoverable, All Other	35,000
Letters of Credit Outstanding, Amount	$ 66,000
Number of Reinsurers Covering Majority	3
Percentage of Ceded Reinsurance Recoverable Represented by Top Three	66.10%
Uncollateralized Credit Exposure Supoorted by Unlimited Uncapped Indemnity	$ 43,000	44,000
Deferred Ceded Premiums And Reinsurance Recoverables	$ 509,000
Reinsurance, Reinsured Risk, Percentage	70%
Financial Guarantee
Summary of Ceded Par and Net Unsecured Reinsurance Recoverable [Line Items]
Letters of Credit Outstanding, Amount	$ 38,000
Specialty Property & Casualty Program
Summary of Ceded Par and Net Unsecured Reinsurance Recoverable [Line Items]
Letters of Credit Outstanding, Amount	28,000
Financial Guarantee
Summary of Ceded Par and Net Unsecured Reinsurance Recoverable [Line Items]
Ceded Loss And Loss Expenses Paid Not Yet Recovered	0	$ (1,000)
QBE Insurance Corporation | Property and Casualty, Commercial Insurance | Standard & Poor's, A Rating
Summary of Ceded Par and Net Unsecured Reinsurance Recoverable [Line Items]
Reinsurance Recoverables, Gross	37,000
Unsecured Reinsurance Recoverables	37,000
Assured Guaranty Re Ltd | Financial Guarantee | Standard & Poor's, AA Rating
Summary of Ceded Par and Net Unsecured Reinsurance Recoverable [Line Items]
Reinsurance Recoverables, Gross	22,000
Unsecured Reinsurance Recoverables	0
General Reinsurance Company | Property and Casualty, Commercial Insurance | Standard & Poor's, AA+ Rating
Summary of Ceded Par and Net Unsecured Reinsurance Recoverable [Line Items]
Reinsurance Recoverables, Gross	123,000
Unsecured Reinsurance Recoverables	$ 104,000

Insurance Contracts - Premium E

Insurance Contracts - Premium Earned (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Insurance [Line Items]
Premiums Earned, Net	$ 33	$ 15	$ 66	$ 29
Direct Premiums Written	93	55	174	115
Direct Premiums Earned	79	52	154	98
Assumed Reinsurance Premiums Written	20	0	38	0
Assumed Reinsurance Premiums Earned	17	0	33	0
Ceded Premiums Written	79	100	150	142
Ceded Reinsurance Premiums Earned	64	37	121	69
Premiums Written, Net	34	(45)	62	$ (27)
Premiums Receivable, Net	$ 317		$ 317		$ 290
Estimated Future Premium Payments Weighted Average Discounted Rate	3.20%		3.20%		3.20%
Weighted average period of future premiums			7 years 7 months 6 days	8 years
Reportable Geographical Components [Member] | United States [Member]
Insurance [Line Items]
Premiums Earned, Net	$ 30	12	$ 60	$ 23
Reportable Geographical Components [Member] | United Kingdom [Member]
Insurance [Line Items]
Premiums Earned, Net	3	3	5	5
Reportable Geographical Components [Member] | Other International [Member]
Insurance [Line Items]
Premiums Earned, Net	$ 0	$ 1	$ 1	$ 1

Derivative Instruments - Summar

Derivative Instruments - Summary of Gross Fair Values of Individual Derivative Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 18	$ 23
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	18	26
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	26	35
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	25
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities		35
Net Amount, Derivative Assets	18	26
Derivative Asset, Fair Value, Gross Asset	18	26
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	26	35
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liabilities Net Amount	0	0
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	18	25
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	25	35
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	25	35
Net Amount, Derivative Assets	18	25
Derivative Asset, Fair Value, Gross Asset	18	25
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	25	35
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liabilities Net Amount	0	0
Warrants [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	1	1
Derivative Asset, Fair Value, Gross Asset	1	1
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Foreign Exchange Future
Derivatives, Fair Value [Line Items]
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
Derivative liabilities	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	0
Derivative Liabilities Net Amount	0
Variable Interest Entity, Primary Beneficiary [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	208	226
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	208	226
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,136	1,197
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0
Gross Amount of Collateral Received/Pledged Not Offset in the Consolidated Balance Sheet, Derivative Liabilities		0
Net Amount, Derivative Assets	0	0
Derivative Asset, Fair Value, Gross Asset	208	226
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	1,136	1,197
Derivative Liability, Fair Value, Amount Offset Against Collateral	0	0
Derivative Liabilities Net Amount	1,136	1,197
Variable Interest Entity, Primary Beneficiary [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	174	190
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	174	190
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet, Derivative Liabilities	1,136	1,197
Net Amount, Derivative Assets	0	0
Derivative Asset, Fair Value, Gross Asset	174	190
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Derivative liabilities	1,136	1,197
Derivative Liabilities Net Amount	1,136	1,197
Variable Interest Entity, Primary Beneficiary [Member] | Currency Swaps [Member]
Derivatives, Fair Value [Line Items]
Net Amounts of Assets Presented in the Consolidated Balance Sheet, Derivative Assets	34	36
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	34	36
Net Amount, Derivative Assets	0	0
Derivative Asset, Fair Value, Gross Asset	34	$ 36
Derivative Asset, Fair Value, Amount Offset Against Collateral	$ 0

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
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	$ 18,000		$ 18,000		$ 23,000
Gains in change in fair value of the call options	0	$ 0	2,000	$ (3,000)
Net liability fair value of all derivative instruments linked to Ambac's own credit risk	25,000		25,000		35,000
Fair value of posted assets as collateral	44,000		44,000		50,000
Derivative assets	18,000		18,000		26,000
Variable Interest Entity, Primary Beneficiary [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative assets	208,000		208,000		226,000
Warrants [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative assets	$ 1,000		$ 1,000		$ 1,000

Derivative Instruments - Summ_2

Derivative Instruments - Summary of Location and Amount of Gains and Losses of Derivative Contracts (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 0	$ 0	$ 2,000	$ (3,000)
Derivative, Gain (Loss) on Derivatives, Total Net	44,000	97,000	61,000	(8,000)
Net gains (losses) on derivative contracts [Domain] | Interest Rate Swap [Member]
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	1,000	1,000	2,000	(3,000)
Net gains (losses) on derivative contracts [Domain] | Warrants [Member]
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0	0	0
Net gains (losses) on derivative contracts [Domain] | Foreign Exchange Future
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0		0
Income Loss On Variable Interest Entities [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	44,000	96,000	59,000	(5,000)
Income Loss On Variable Interest Entities [Member] | Interest Rate Swap [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	43,000	97,000	57,000	(2,000)
Income Loss On Variable Interest Entities [Member] | Currency Swaps [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Debt and Equity Securities, FV-NI [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 0	$ (1,000)	$ 2,000	$ (3,000)

Derivative Instruments - Summ_3

Derivative Instruments - Summary of Notional Amounts of AFS's Trading Derivative Products (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
AFS [Member] | Interest Rate Swap [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	$ 159	$ 167
AFS [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	140	141
Variable Interest Entity, Primary Beneficiary [Member] | Interest Rate Swap [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	1,648	1,662
Variable Interest Entity, Primary Beneficiary [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	$ 820	$ 864

Derivative Instruments - Summ_4

Derivative Instruments - Summary of Notional for VIE Derivatives Outstanding (Details) - Variable Interest Entity, Primary Beneficiary [Member] - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Interest Rate Swap [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	$ 1,648	$ 1,662
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	820	864
Currency Swaps [Member]
Schedule Of Loans And Allowance For Loan By Class Individually And Collectively Evaluated For Impairment [Line Items]
Derivative products, Notional Amount	$ 136	$ 149

Intangible Assets (Details)

Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Intangible assets, less accumulated amortization	$ 285,000		$ 285,000		$ 307,000
Amortization of Intangible Assets	8,000	$ 7,000	21,000	$ 13,000
Finite-Lived Intangible Assets, Net	271,000		271,000		292,000
PWIC
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	14,000		14,000		14,000
Insurance Intangible Asset [Member]
Intangible Assets, Gross (Excluding Goodwill)	1,256,000		1,256,000		1,258,000
Finite-Lived Intangible Assets, Accumulated Amortization	1,030,000		1,030,000		1,013,000
Intangible assets, less accumulated amortization	226,000		226,000		245,000
Other Intangible Assets
Intangible Assets, Gross (Excluding Goodwill)	57,000		57,000		57,000
Finite-Lived Intangible Assets, Accumulated Amortization	12,000		12,000		10,000
Intangible assets, less accumulated amortization	$ 45,000		$ 45,000		$ 47,000

Special Purpose Entities, Inc_2

Special Purpose Entities, Including Variable Interest Entities - Additional Information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($) Entity consolidationVIE	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) Entity	Jun. 30, 2023 USD ($) consolidationVIE	Dec. 31, 2023 USD ($) Entity
Variable Interest Entities [Line Items]
Variable Interest Entity Change in Fair Value of Assets and Liabilities	$ 0	$ 0	$ 1,000,000	$ 2,000,000
Revenue from Contract with Customer, Excluding Assessed Tax	13,000,000	10,000,000	31,000,000	25,000,000
Realized Investment Gains (Losses)	4,000,000	(3,000,000)	4,000,000	(8,000,000)
Other Operating Income (Expense), Net	16,000,000	2,000,000	18,000,000	5,000,000
Fair value of special purpose entities	0		0
Variable Interest Entity, Measure of Activity, Income or Loss before Tax	0	$ 0	2,000,000	$ (1,000,000)
Long-term debt	$ 515,000,000		515,000,000		$ 508,000,000
Number of Variable Interest Entities Consolidated During the Period	0	0
Number of Variable Interest Entities Deconsolidated During Period | consolidationVIE	0			1
Gain (loss) from consolidating VIEs	$ 0	$ 0	0	$ 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	$ 45,000,000		$ 45,000,000		$ 40,000,000
Consolidated Entities [Member]
Variable Interest Entities [Line Items]
Number Of Consolidated Variable Interest Entities | Entity	6		6		6
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Reclassification Adjustment from AOCI for Derecognition, before Tax	$ 0	1,000,000	$ 0	1,000,000
VIE Change in FV of Assets Liabilities, Net of Credit Risk Change	1,000,000	0	2,000,000	3,000,000
Gross Investment Income, Operating	2,000,000	3,000,000
Revenue from Contract with Customer, Excluding Assessed Tax	3,000,000		8,000,000
Interest Expense, Long-term Debt	(4,000,000)	(3,000,000)	(6,000,000)	(8,000,000)
Other Operating Income (Expense), Net	3,000,000	0	7,000,000	0
Long-term debt	$ 2,853,000,000		$ 2,853,000,000		$ 2,967,000,000
Ambac UK [Member] | Consolidated Entities [Member]
Variable Interest Entities [Line Items]
Number Of Consolidated Variable Interest Entities | Entity	4		4		4
Ambac UK [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Long-term debt	$ 2,696,000,000		$ 2,696,000,000		$ 2,808,000,000
Ambac Assurance [Member] | Consolidated Entities [Member]
Variable Interest Entities [Line Items]
Number Of Consolidated Variable Interest Entities | Entity	2		2		2
Ambac Assurance [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Long-term debt	$ 156,000,000		$ 156,000,000		$ 159,000,000
Fixed Income Investments [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Gross Investment Income, Operating			5,000,000	5,000,000
Realized Investment Gains (Losses)	$ 0	$ 0	$ 0	$ 0

Special Purpose Entities, Inc_3

Special Purpose Entities, Including Variable Interest Entities - Summary of Fair Value of Fixed Income Securities, by Asset-Type, Held by Consolidated Variable Interest Entities (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Variable Interest Entities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 2,078	$ 2,197
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	45	40
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	78	71
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Loans Unpaid Principal Balance	1,692	1,787
Long Term Debt Unpaid Principal Balance	2,854	2,952
Variable Interest Entity, Primary Beneficiary [Member] | Municipal Bonds [Member]
Variable Interest Entities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	85	88
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	6	7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	$ 0	$ 0

Special Purpose Entities, Inc_4

Special Purpose Entities, Including Variable Interest Entities - Supplemental Information about Loans Held as Assets and Long-Term Debt Associated with Consolidated Variable Interest Entities (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Variable Interest Entities [Line Items]
Long-term debt	$ 515	$ 508
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Long-term debt	2,853	2,967
Long-term debt, Estimated fair value	2,599	2,710
Loans Unpaid Principal Balance	1,692	1,787
Long Term Debt Unpaid Principal Balance	$ 2,854	$ 2,952

Special Purpose Entities, Inc_5

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 (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	$ 20,109	$ 20,861
Insurance Assets	331	351
Insurance Liabilities	742	836
Derivative Liabilities	0
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entities [Line Items]
Derivative Liabilities		0
Global Public Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	17,101	17,498
Insurance Assets	204	209
Insurance Liabilities	196	202
Derivative Liabilities	0	0
Global Structured Finance [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	3,007	3,364
Insurance Assets	127	141
Insurance Liabilities	546	634
Derivative Liabilities	0	0
Global Structured Finance [Member] | Residential Mortgage-Backed Securities [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	2,224	2,391
Insurance Assets	123	135
Insurance Liabilities	409	432
Derivative Liabilities	0	0
Global Structured Finance [Member] | Other Consumer Asset-Backed [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	365	540
Insurance Assets	3	5
Insurance Liabilities	135	200
Derivative Liabilities	0	0
Global Structured Finance [Member] | Other [Member]
Variable Interest Entities [Line Items]
Maximum Exposure To Loss	418	433
Insurance Assets	2	2
Insurance Liabilities	2	2
Derivative Liabilities	$ 0	$ 0

Variable Interest Entities Spec

Variable Interest Entities Special Purpose Entities, including Variable Interest Entities - Summary of Assets and Liabilities (Details) $ in Millions	Jun. 30, 2024 USD ($) Entity	Dec. 31, 2023 USD ($) Entity	Jun. 30, 2023 USD ($)
Debt Securities, Available-for-sale, Amortized Cost	$ 2,078	$ 2,197
Fixed maturity securities, at fair value	2,043
Restricted Cash	11	12	$ 10
Derivative assets	18	26
Other assets	163	129
Total assets	8,184	8,428	8,132
Interest Payable	500	475
Long-term debt	515	508
Derivative Liability	26	35
Other Liabilities	203	199
Liabilities	6,748	6,997
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	45	40
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	78	71
Variable Interest Entity, Primary Beneficiary [Member]
Fixed maturity securities, at fair value	2,101	2,167
Restricted Cash	62	246	$ 266
Financing Receivable, after Allowance for Credit Loss	1,567	1,663
Derivative assets	208	226
Other assets	95	92
Total assets	4,033	4,394
Long-term debt	2,599	2,710
Long-term Debt, at par less amortized discount	253	258
Long-term debt	2,853	2,967
Derivative Liability	1,136	1,197
Other Liabilities	7	5
Liabilities	4,048	4,404
Estimated Future Premium Payments Maximum Discounted Rate	52	235
Variable Interest Entity, Primary Beneficiary [Member] | Corporate Debt Securities [Member]
Fixed maturity securities, at fair value	2,010	2,072
Variable Interest Entity, Primary Beneficiary [Member] | Municipal Bonds [Member]
Debt Securities, Available-for-sale, Amortized Cost	85	88
Fixed maturity securities, at fair value	91	95
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	6	7
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Ambac UK [Member]
Fixed maturity securities, at fair value	2,010	2,072
Restricted Cash	61	245
Financing Receivable, after Allowance for Credit Loss	1,567	1,663
Derivative assets	208	226
Other assets	93	90
Total assets	3,939	4,296
Long-term debt	2,599	2,710
Long-term Debt, at par less amortized discount	97	99
Long-term debt	2,696	2,808
Derivative Liability	1,136	1,197
Cash collateral payable	52
Other Liabilities	6	4
Liabilities	3,890	4,244
Estimated Future Premium Payments Maximum Discounted Rate		235
Variable Interest Entity, Primary Beneficiary [Member] | Ambac UK [Member] | Corporate Debt Securities [Member]
Fixed maturity securities, at fair value	2,010	2,072
Variable Interest Entity, Primary Beneficiary [Member] | Ambac UK [Member] | Municipal Bonds [Member]
Fixed maturity securities, at fair value	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Ambac Assurance [Member]
Fixed maturity securities, at fair value	91	95
Restricted Cash	1	1
Financing Receivable, after Allowance for Credit Loss	0	0
Derivative assets	0	0
Other assets	2	2
Total assets	94	98
Long-term debt	0	0
Long-term Debt, at par less amortized discount	156	159
Long-term debt	156	159
Derivative Liability	0	0
Other Liabilities	1	1
Liabilities	157	160
Estimated Future Premium Payments Maximum Discounted Rate	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Ambac Assurance [Member] | Corporate Debt Securities [Member]
Fixed maturity securities, at fair value	0	0
Variable Interest Entity, Primary Beneficiary [Member] | Ambac Assurance [Member] | Municipal Bonds [Member]
Fixed maturity securities, at fair value	$ 91	$ 95
Consolidated Entities [Member]
Number Of Consolidated Variable Interest Entities | Entity	6	6
Consolidated Entities [Member] | Ambac UK [Member]
Number Of Consolidated Variable Interest Entities | Entity	4	4
Consolidated Entities [Member] | Ambac Assurance [Member]
Number Of Consolidated Variable Interest Entities | Entity	2	2

Revenue Recognition and Defer_2

Revenue Recognition and Deferred Revenue (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Contract with Customer, Liability, Revenue Recognized		$ 1	$ 0
Revenue from Contract with Customer, Excluding Assessed Tax	$ 13	10	31	$ 25
Contract with Customer, Asset, after Allowance for Credit Loss	101		101		$ 95
Contract with Customer, Liability	0		0		1
Variable Interest Entity, Primary Beneficiary [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	3		8
Contract with Customer, Asset, after Allowance for Credit Loss	90		90		87
Contract with Customer, Performance Obligation Satisfied in Previous Period			9	5
Managing General Agency Underwriter
Contract with Customer, Asset, after Allowance for Credit Loss	11		11		$ 7
Employer Stop Loss
Revenue from Contract with Customer, Excluding Assessed Tax	2	2	7	7
Affinity Products
Revenue from Contract with Customer, Excluding Assessed Tax	5	5	10	10
Commercial Auto
Revenue from Contract with Customer, Excluding Assessed Tax	3	2	7	5
Product and Service, Other
Revenue from Contract with Customer, Excluding Assessed Tax	0	0	0	0
Marine
Revenue from Contract with Customer, Excluding Assessed Tax	1	1	2	2
Professional Liability
Revenue from Contract with Customer, Excluding Assessed Tax	$ 2	$ 0	$ 4	$ 0
Minimum [Member]
Employee Stop Loss Time When Base Commissions Recognized Begin and End In Months	17
Maximum [Member]
Employee Stop Loss Time When Base Commissions Recognized Begin and End In Months	20

Comprehensive Income - Schedule

Comprehensive Income - Schedule of Changes in Balances of Each Component of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	$ (175)	$ (217)	$ (160)	$ (253)
Other comprehensive income before reclassifications	(9)	(6)	5	(39)
Amounts reclassified from accumulated other comprehensive income	(9)	2	(10)	5
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	0	8	(15)	44
Ending Balance	(175)	(209)	(175)	(209)
Income Tax Expense (Benefit)	2	2	7	6
Realized Investment Gains (Losses)	4	(3)	4	(8)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(27)	(54)	(20)	(71)
Other comprehensive income before reclassifications	(8)	15	(1)	1
Amounts reclassified from accumulated other comprehensive income	(4)	3	(5)	6
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	4	(13)	(3)	5
Ending Balance	(23)	(67)	(23)	(67)
Realized Investment Gains (Losses)	(4)	3	(4)	8
Accumulated Translation Adjustment [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(152)	(168)	(144)	(184)
Other comprehensive income before reclassifications	(1)	(21)	7	(37)
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1	21	(7)	37
Ending Balance	(151)	(147)	(151)	(147)
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	(1)	(1)	(1)	(1)
Other comprehensive income before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income	0	0	0	0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	0	0	0	0
Ending Balance	(1)	(1)	(1)	(1)
Other Postretirement Benefits Plan [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Beginning Balance	5	6	5	3
Other comprehensive income before reclassifications	0	0	0	(3)
Amounts reclassified from accumulated other comprehensive income	(5)	0	(5)	(1)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(5)	0	(5)	2
Ending Balance	0	6	0	6
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Income Tax Expense (Benefit)	0	(1)	0	(2)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Income Tax Expense (Benefit)			0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Other Postretirement Benefits Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	0	0	0	0
Changes In Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from accumulated other comprehensive income	(5)	0	(5)	(1)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	0	0	0	0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(5)	0	(5)	(1)
Income Tax Expense (Benefit)	$ 0	$ 0	$ 0	$ 0

Comprehensive Income - Schedu_2

Comprehensive Income - Schedule of Amounts Reclassed Out of Each Component of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	$ (2)	$ (2)	$ (7)	$ (6)
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, after Tax	0	0	0	0
Net of tax and noncontrolling interest	(1)	(13)	19	(47)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(9)	2	(10)	5
Realized Investment Gains (Losses)	4	(3)	4	(8)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax and noncontrolling interest	(4)	3	(5)	6
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(4)	3	(5)	6
Realized Investment Gains (Losses)	(4)	3	(4)	8
Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, Unrealized Gain (Loss) Arising During Period, after Tax	0	0	0	0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	0	0
Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, before Tax, after Reclassification Adjustment	0	(1)	0	0
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax and noncontrolling interest	(9)	2	(9)	5
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	1	0	2
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)			0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Gain (Loss), Financial Liability, Fair Value Option, Including Portion Attributable to Noncontrolling Interest [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	0	0		0
Other Postretirement Benefits Plan [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(5)	0	(5)	(1)
Other Postretirement Benefits Plan [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense (benefit)	0	0	0	0
Prior service cost	0	0	0	0
Actuarial gains (losses)	0	0	0	0
Other Comprehensive Income (Loss), Defined Benefit Plan, Settlement and Curtailment Gain (Loss), after Tax	5		5
Total before tax	(5)	0	(5)	(1)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ (5)	$ 0	$ (5)	$ (1)

Net Income Per Share - Addition

Net Income Per Share - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2024	Jun. 30, 2023	Apr. 30, 2013
Schedule Of Earnings Per Share [Line Items]
Common stock, shares outstanding	45,224,972			45,224,972
Par value of common stock issued	$ 0.01			$ 0.01		$ 0.01
Earnings Per Share, Basic	(0.02)	$ (0.29)		0.42	$ (1.02)
Earnings Per Share, Diluted	$ (0.02)	$ (0.29)		$ 0.41	$ (1.02)
Noncontrolling Interest, Change in Redemption Value	$ 0	$ 0	$ 0	$ 0	$ 0
Net Income (Loss) Available to Common Stockholders, Basic	$ (1)	$ (13)		$ 19	$ (47)
Common Stock [Member]
Schedule Of Earnings Per Share [Line Items]
Number of new common stock issued				29,602

Net Income Per Share - Reconcil

Net Income Per Share - Reconciliation of Common Shares Used for Basic and Diluted Earnings Per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average number of common shares used for basic earnings per share	46,209,250	45,757,234	46,019,145	45,661,288
Effect of potential dilutive shares:
Weighted average number of common shares and potential dilutive shares used for diluted earnings per share	46,209,250	45,757,234	46,568,862	45,661,288
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	0	0	0
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	471,541	556,602	44,362	555,981
Performance Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	464,272	667,365	0	667,365
Restricted Stock Units (RSUs) [Member]
Effect of potential dilutive shares:
Effect of potential dilutive shares	0	0	158,132	0
Performance Shares [Member]
Effect of potential dilutive shares:
Effect of potential dilutive shares	0	0	391,585	0

Net Income Per Share Schedule o

Net Income Per Share Schedule of Basic and Dilutive Securities for EPS (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Weighted Average Number of Shares Outstanding, Basic	46,209,250	45,757,234	46,019,145	45,661,288
Weighted Average Number of Shares Outstanding, Diluted	46,209,250	45,757,234	46,568,862	45,661,288
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	471,541	556,602	44,362	555,981
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	0	0	0
Performance Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	464,272	667,365	0	667,365
Performance Shares [Member]
Weighted Average Number Diluted Shares Outstanding Adjustment	0	0	391,585	0
Restricted Stock Units (RSUs) [Member]
Weighted Average Number Diluted Shares Outstanding Adjustment	0	0	158,132	0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details)	3 Months Ended
	Jun. 30, 2024
Minimum [Member]
Tax Credit Carryforward [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2030
Maximum [Member]
Tax Credit Carryforward [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2042

Income Taxes Income Taxes - Pro

Income Taxes Income Taxes - Provision for Income Taxes Charged To Income From Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Provision for Income Taxes [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Domestic	$ (11)	$ (18)	$ (1)	$ (66)
Current Income Tax Expense (Benefit)	2	2	7	4
Deferred Foreign Income Tax Expense (Benefit)	0	0	1	2
Deferred Income Tax Expense (Benefit)	0	0	1	2
Income Tax Expense (Benefit)	2	2	7	6
Income (Loss) from Continuing Operations before Income Taxes, Foreign	13	7	28	26
Current State and Local Tax Expense (Benefit)	0	0	0	0
Current Foreign Tax Expense (Benefit)	2	0	7	2
Current Federal Tax Expense (Benefit)	$ 0	$ 1	$ 0	$ 1

Income Taxes Income Taxes - NOL

Income Taxes Income Taxes - NOL Usage Table (Details) $ in Millions	3 Months Ended
	Jun. 30, 2024 USD ($)
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	$ 3,532
Domestic Tax Authority [Member] | Interest Expense
Net Income Loss Reconciliation [Line Items]
NOL allocated amount	$ 186
Minimum [Member]
Net Income Loss Reconciliation [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2030
Maximum [Member]
Net Income Loss Reconciliation [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2042

Income Taxes Schedule of Income

Income Taxes Schedule of Income Before Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Schedule of Income Before Income Tax, Domestic and Foreign [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Domestic	$ (11)	$ (18)	$ (1)	$ (66)
Income (Loss) from Continuing Operations before Income Taxes, Foreign	13	7	28	26
Pretax income (loss)			27	(40)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ 2	$ (11)	$ 27	$ (40)

Compensation Related Costs, P_2

Compensation Related Costs, Postemployment Benefits (Details) $ in Millions	3 Months Ended
	Jun. 30, 2024 USD ($)
Postemployment Benefits, Period Expense	$ 13

Uncategorized Items - ambc-2024

Label	Element	Value
Goodwill, Impairment Loss	us-gaap_GoodwillImpairmentLoss	$ 0
Goodwill, Impairment Loss	us-gaap_GoodwillImpairmentLoss	0
Goodwill, Acquired During Period	us-gaap_GoodwillAcquiredDuringPeriod	0
Goodwill, Acquired During Period	us-gaap_GoodwillAcquiredDuringPeriod	$ 9,000,000