Change in net unrealized gains (losses) on: OCI, Debt Securities, Available-for-Sale, Gain (Loss), before Adjustment, after Tax [Abstract] Foreign exchange gains (losses) on remeasurement of certain assets and liabilities Foreign Exchange Gains (Losses) on Remeasurment of Premiums Receivable and Loss [Member] Foreign Exchange Gains (Losses) on Remeasurment of Premiums Receivable and Loss Debt and Equity Securities, FV-NI [Line Items] Debt and Equity Securities, FV-NI [Line Items] Change in discount rates on future policy benefits for annuity reinsurance contracts, tax OCI, Liability for Future Policy Benefit, Gain (Loss), after Reclassification Adjustment, Tax Net realized investment gains (losses) Realized Investment Gains (Losses) Entity Listings, Exchange [Axis] Entity Listings, Exchange [Axis] CDR Measurement Input, Default Rate [Member] Award Timing Predetermined Award Timing Predetermined [Flag] Entity File Number Entity File Number Credit Risk Contract Credit Risk Contract [Member] Deferred premium revenue Financial Guarantee Insurance Contracts, Premium Received over Contract Period, Unearned Premium Revenue AAA Internal Investment Grade, AAA [Member] The entity's internal risk assessment category, AAA, representing the second lowest risk level. 1 Tabular List, Table Tabular List [Table Text Block] 2026 (July 1 - September 30) Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Third Quarter Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Third Quarter Aircraft residual value insurance (RVI) Aircraft residual value insurance (RVI) 3721 Aircraft [Member] Recent Accounting Standards Not Yet Adopted New Accounting Pronouncements, Policy [Policy Text Block] Purchases Payments to Acquire Short-Term Investments Share value, amount Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Share Value, Amount Value of business acquired Business Combination, Value Of Business Acquired Business Combination, Value Of Business Acquired Fair Value, by Balance Sheet Grouping, Disclosure Item Amounts [Axis] Measurement Basis [Axis] Adjustment to Compensation: Adjustment to Compensation [Axis] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Other Comprehensive Income (Loss) Other Comprehensive Income (Loss) [Member] 2027 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Year Two Total Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate [Abstract] Due after 10 years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost Policyholder Account Balance [Roll Forward] Policyholder Account Balance [Roll Forward] Percent of Total Percentage of Available-for-sale Securities at Amortized Cost Represents individual investment categories as a percentage of the aggregate amortized cost of investments. Securities purchased with credit deterioration Debt Securities, Available-for-Sale, Purchased with Credit Deterioration, Amount at Purchase Price Adjustment to Compensation, Amount Adjustment to Compensation Amount Number of fixed maturity securities valued using model processes Available-for-sale Debt Securities, Number of Instruments Represents the number of fixed maturity securities and short-term investments which have been valued using model processes set by the entity. Percentage of installment premiums denominated in currencies other than the U.S. dollar Concentration Risk, Percentage Consolidation Consolidation, Policy [Policy Text Block] Employee Stock Option Share-Based Payment Arrangement, Option [Member] Market multiple-price to earnings Measurement Input, Price to Earnings [Member] Measurement Input, Price to Earnings Dividends Dividends, Common Stock, Cash Total shareholders’ equity attributable to Assured Guaranty Ltd. Equity, Attributable to Parent Measurement Frequency [Axis] Measurement Frequency [Axis] Insider Trading Policies and Procedures [Line Items] 2046-2050 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year 20 Through 25 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year 20 Through 25 Common stock, shares authorized (in shares) Common Stock, Shares Authorized FG VIEs’ liabilities Liabilities, Fair Value Measurement Input Liabilities, Fair Value Measurement Input Recurring Fair Value, Recurring [Member] Liabilities Liabilities and Equity [Abstract] Net Earned Premiums Financial Guarantee Insurance Contracts, Net Earned Premiums [Table Text Block] Tabular disclosure of the net premium earned with respect to financial guarantee insurance contracts. Funds withheld, at fair value Funds Held under Reinsurance Agreements, Asset Premiums receivable, net of commissions payable, net of allowance for credit losses of $3 and $3 Premiums Receivable, Net Cover [Abstract] Cover [Abstract] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Maximum Maximum [Member] Policyholder Account Balance, above Guaranteed Minimum Crediting Rate [Domain] Policyholder Account Balance, above Guaranteed Minimum Crediting Rate [Domain] Investments, unfunded commitment Alternative Investments, Unfunded Commitment Alternative Investments, Unfunded Commitment Effect of changes in discount rate assumptions AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax Accretion of Discount Premiums Receivable Accretion Of Discount [Abstract] Premiums Receivable Accretion Of Discount Less: Noncontrolling interest Net Income (Loss) Attributable to Noncontrolling Interest Future policy benefits for annuity reinsurance contracts (including deferred profit liability) Business Combination, Recognized Liability Assumed, Future Policy Benefits Business Combination, Recognized Liability Assumed, Future Policy Benefits Fair Value Debt Securities, Available-for-Sale, Unrealized Loss Position Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Change in unrealized gains/(losses) included in earnings related to financial instruments Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss) Expected cash outflows (inflows) Schedule of Insured Financial Obligations with Credit Deterioration, Expected Cash Flows [Abstract] -- None. No documentation exists for this element. -- Global minimum tax rate, percent Effective Income Tax Rate Reconciliation, Global Minimum Tax Rate, Percent Effective Income Tax Rate Reconciliation, Global Minimum Tax Rate, Percent Total Earnings Of Deferred Premium Revenue, Net [Abstract] Earnings Of Deferred Premium Revenue, Net Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] 2026 (July 1 - September 30) Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Third Quarter Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Deferred Loan Recovery Scenario [Axis] Deferred Loan Recovery Scenario [Axis] Deferred Loan Recovery Scenario Total Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Total Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Total Bargain purchase gain Business Combination, Bargain Purchase, Gain Recognized, Amount Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] 2051-2055 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year 25 Through 30 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year 25 Through 30 Others Other Asset Backed Securities [Member] Other Asset Backed Securities [Member] Net sales (purchases) of short-term investments with original maturities of less than three months Payments for (Proceeds from) Short-term Investments, with Maturities of Less Than Three Months Payments for (Proceeds from) Short-term Investments, with Maturities of Less Than Three Months Income (loss) before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Entity Shell Company Entity Shell Company Gross Schedule of Insured Financial Obligations with Credit Deterioration, Net Claim Liability, Undiscounted, Direct Assumed Schedule of Insured Financial Obligations with Credit Deterioration, Net Claim Liability, Undiscounted, Direct Assumed Future policy benefits for annuity reinsurance contracts Liability for Future Policy Benefit, after Reinsurance Recourse Status [Domain] Recourse Status [Domain] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Operating Segments Operating Segments [Member] Expected Loss to be Paid (Recovered) Expected Loss to be Paid [Text Block] Expected Loss to be Paid [Text Block] AGC Assured Guaranty Inc [Member] Represents principal insurance company subsidiary, Assured Guaranty Inc. Less: Comprehensive income (loss) attributable to noncontrolling interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Interest expense Interest Expense, Operating Reclassification out of Accumulated Other Comprehensive Income [Table] Reclassification out of Accumulated Other Comprehensive Income [Table] Other invested assets Other Invested Assets [Member] Represents other invested assets not separately disclosed. 2031-2035 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, after Year 5 Through 10 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, after Year 5 Through 10 Document Fiscal Period Focus Document Fiscal Period Focus Credit for estimated future recoveries of claims paid Public Finance Estimated Future Recoveries of Claims Paid Public Finance Estimated Future Recoveries of Claims Paid Award Timing Method Award Timing Method [Text Block] Litigation Case [Domain] Litigation Case [Domain] Award Type Award Type [Axis] Cumulative Translation Adjustment Accumulated Foreign Currency Adjustment Attributable to Parent [Member] 2027 Financial Guarantee Insurance Contracts, Future Expected, Net Loss to be Expensed in First Full Fiscal Year Financial Guarantee Insurance Contracts, Future Expected, Net Loss to be Expensed in First Full Fiscal Year Projected loss assumptions, increase (decrease) in expected loss to be paid, net Guarantor Obligations, Projected Loss Assumptions, Increase (Decrease) in Expected Loss to be Paid Net Represents the change in expected loss on a pool of insured obligations that would result from an increase in the conditional default rate plateau period and loss severity recovery period. Plaintiff, terminated board members Loss Contingency, Plaintiff, Terminated Board Members Loss Contingency, Plaintiff, Terminated Board Members Investment, Name [Domain] Investment, Name [Domain] Trading Symbol Trading Symbol Share-based compensation (in shares) Stock Issued During Period, Shares, Share-based Compensation and Other Number of shares issued during the period as a result of net share activity under the company's long-term incentive plan, employee stock purchase plan, and share cancellations in satisfaction of withholding tax requirements. Credit Impairment AOCI, Gain (Loss), Debt Securities, Available-for-Sale, with Allowance for Credit Loss, Parent [Member] Entity Address, City or Town Entity Address, City or Town Gross Schedule of Insured Financial Obligations with Credit Deterioration, Reductions of Gross Claim Liability, Gross Potential Recoveries Fair value gains (losses) on trading securities Debt Securities, Trading, Unrealized Gain (Loss) Effect of foreign exchange rate changes Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Statement of Income Location, Balance [Domain] Statement of Income Location, Balance [Domain] Policyholder Account Balance, above Guaranteed Minimum Crediting Rate [Axis] Policyholder Account Balance, above Guaranteed Minimum Crediting Rate [Axis] Weighted average risk-free rates for U.S. dollar denominated financial guaranty insurance obligations Financial Guarantee Insurance Contract, Claim Liability, Weighted-Average Risk-Free Discount Rate Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Loss and LAE Reserve and Salvage and Subrogation Recoverable Net of Reinsurance Insurance Contracts Liability for Unpaid Claims and Claims Adjustment Expense and Salvage and Subrogation Recoveries [Table Text Block] Tabular disclosure of the reserve for settling insured claims and expenses incurred in the claims settlement process, net of reinsurance, including salvage and subrogation recoverable amounts. Entity Emerging Growth Company Entity Emerging Growth Company Outstanding Exposure Disclosure [Abstract] Outstanding Exposure Disclosure [Abstract] Outstanding Exposure Disclosure [Abstract] Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Earnings of Deferred Premium Revenue Future Net Premiums to be Earned [Abstract] Future Net Premiums to be Earned Fair value gains (losses) on derivatives Fair value gains (losses) on derivatives Derivative, Gain (Loss) on Derivative, Net Fixed-Maturity Securities, Trading Fixed Maturities, Trading Securities [Member] Fixed Maturities, Trading Securities Net Expected Loss to be Paid After Net Expected Recoveries for Breaches of R&W Roll Forward Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid Roll Forward [Table Text Block] Tabular disclosure of a roll forward of the present value of net expected loss and LAE to be paid for financial guaranty contracts accounted for as insurance by sector. Expected loss to be paid is the Company's estimate of the present value of future claim payments, net of reinsurance and net of salvage and subrogation which includes the present value benefit of estimated recoveries for breaches of R&W. After 2055 Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, after Year 30 Through 35 Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Insurance [Abstract] Insurance [Abstract] Contra-paid, net Financial Guarantee Insurance Contracts Paid But Unexpensed Losses Net Amount of losses paid and not yet expensed on financial guaranty insurance contracts, net of ceded amounts. Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Marketable Securities Marketable Securities [Table Text Block] Other assets, fair value disclosure Other assets Other Assets, Fair Value Disclosure Expected future benefit payments, undiscounted Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance Net expected loss to be paid Schedule of Insured Financial Obligations with Credit Deterioration, Net Claim Liability, Net of Reinsurance Recoverable Schedule of Insured Financial Obligations with Credit Deterioration, Net Claim Liability, Net of Reinsurance Recoverable Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Number of risks, credit derivative Financial Guaranty Contracts Accounted for as Credit Derivatives Number of Contracts Represents the number of unique credits in the insured portfolio accounted for as credit derivative. Pledged Status [Domain] Pledged Status [Domain] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Restatement Determination Date Restatement Determination Date Assured Life Re Acquisition Assured Life Re Acquisition [Member] Assured Life Re Acquisition Less: Provision (benefit) for income taxes Income Tax Expense (Benefit) Other assets (includes $180 and $174, at fair value) Other assets (including other invested assets) Other Assets Fair value at beginning of period Fair value at end of period Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Interest credited Policyholder Account Balance, Interest Expense Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Policyholder Account Balance, Guaranteed Minimum Crediting Rate Range [Axis] Policyholder Account Balance, Guaranteed Minimum Crediting Rate Range [Axis] Equity method investments Funds and Other investments [Member] Funds and Other investments 2028 Financial Guarantee Insurance Contracts, Future Expected, Net Loss to be Expensed in Second Full Fiscal Year For financial guaranty insurance contracts, the amount of net loss expected to be expensed within the second full fiscal year following the date of the latest balance sheet presented in the financial statements. Loss mitigation securities Insured Financial Obligations, Loss Mitigation Securities Represents the outstanding principal amounts of the securities insured and purchased by the Company, and for which it has expected losses to be paid, in order to mitigate the economic effect of insured losses ("loss mitigation securities"). Deferred equity compensation Compensation and Benefits Trust Schedule of Guarantor Obligations [Table] Guarantor Obligation [Table] Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward] Present Value of Net Expected Loss and Loss Adjustment Expenses to be Paid [Roll Forward] Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Equity, Class of Treasury Stock [Line Items] Equity, Class of Treasury Stock [Line Items] Assured Life Reinsurance, Ltd. acquisition, net of cash acquired (see Note 2) Payments to Acquire Businesses, Net of Cash Acquired All Trading Arrangements All Trading Arrangements [Member] Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Deferred Equity Compensation Deferred Compensation, Share-Based Payments [Member] Class of Treasury Stock [Table] Class of Treasury Stock [Table] Number of securities with unrealized losses greater than 10% of book value for 12 months or more Available-for-sale Securities, Continuous Unrealized Loss Position, Greater than 10 Percent of Book Value, Twelve Months or Longer, Number Represents the number of securities which had unrealized losses greater than 10% of book value for 12 months or more. Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Litigation settlement, gain Litigation Settlement, Gain Five-year CDS spread Credit Risk Contract, 5 Year Spread [Member] Credit Risk Contract, 5 Year Spread [Member] Asset Management Asset Management Segment [Member] Asset Management Segment [Member] Expected Losses [Abstract] Expected Losses [Abstract] Expected Losses [Abstract] Net cash flows provided by (used in) operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Less than 12 months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months [Abstract] Statutory Accounting Practice, Jurisdiction [Axis] Statutory Accounting Practice, Jurisdiction [Axis] Financial guaranty insurance contracts Financial Guaranty Insurance Contracts Net Value This element represents the net financial guaranty contract position for the entity, consisting of premiums receivable, ceded unearned premium reserve, reinsurance recoverable on unpaid losses, salvage and subrogation recoverable, unearned premium reserve, loss and loss adjustment expense reserve, and reinsurance balances payable, net. Sales Proceeds from Sale of Debt Securities, Available-for-Sale Fixed-maturity securities, available-for-sale, at fair value, net of allowance for credit loss of $63 and $54 (amortized cost of $7,241 and $6,572) Fixed-maturity securities, available for sale Estimated fair value Debt Securities, Available-for-Sale, Excluding Accrued Interest 2026 (October 1 - December 31) Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Fourth Quarter Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Fourth Quarter Non-cash compensation and operating expenses Non-cash Compensation and Operating Expenses, Segment Non-cash Compensation and Operating Expenses, Segment Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Paydowns of financial guaranty variable interest entities’ assets Proceeds from Paydowns on Financial Guaranty Variable Interest Entities Assets Proceeds received on paydowns of consolidated variable interest entities assets. The Company consolidates these variable interest entities as the result of its control rights obtained under financial guaranty insurance contracts. Assured Guaranty US Holdings Inc. 6.125% Senior Notes Due 2028 Assured Guaranty US Holdings Inc. 6.125% Senior Notes Due 2028 [Member] Assured Guaranty US Holdings Inc. 6.125% Senior Notes Due 2028 Subsequent Event Subsequent Event [Member] Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] PEO Total Compensation Amount PEO Total Compensation Amount 2029 Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, Year Four Assets purchased: Business Combination, Recognized Asset Acquired, Asset [Abstract] Accelerations from refundings, terminations and modifications Financial Guarantee Insurance Contracts, Accelerated Premium Revenue (Refunds), Amount Financial Guarantee Insurance Contracts, Accelerated Premium Revenue (Refunds), Amount 2029 Financial Guarantee Insurance Contracts, Future Expected, Net Loss to be Expensed in Third Full Fiscal Year Financial Guarantee Insurance Contracts, Future Expected, Net Loss to be Expensed in Third Full Fiscal Year Schedule of Financial Guaranty Exposure by Internal Rating Schedule of Financial Guaranty Exposure by Internal Rating [Table Text Block] Tabular disclosure of the outstanding principal amounts of financial obligations underlying the entity's financial guaranty contracts, net of ceded contracts, by internal credit rating. Weighted average discount rate Guarantor Obligations, Net Expected Loss to be Paid After Recoveries for Representations and Warranties, Weighted Average Discount Rate Guarantor Obligations, Net Expected Loss to be Paid After Recoveries for Representations and Warranties, Weighted Average Discount Rate Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost, Rolling Maturity [Abstract] Equity Components [Axis] Equity Components [Axis] 2046-2050 Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed More than 19 and Within 24 Years from Balance Sheet Date Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed More than 19 and Within 24 Years from Balance Sheet Date Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] 2026 (April 1 - June 30) Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Second Quarter Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Second Quarter Net amount at risk Policyholder Account Balance, Net Amount at Risk Number of reportable segments Number of Reportable Segments Sound Point Agreement Sound Point Agreement [Member] Sound Point Agreement Funds withheld Business Combination, Recognized Asset Acquired, Funds Withheld Business Combination, Recognized Asset Acquired, Funds Withheld Loss and loss adjustment expenses (benefit) Segment loss and loss adjustment expense (LAE) (benefit) Policyholder Benefits and Claims Incurred, Net Variable Interest Entities Variable Interest Entity Disclosure [Text Block] Entity Address, Country Entity Address, Country Number of policies monitored, not within the scope of ASC 810 Variable Interest Entity, Number of Policies Monitored, Not Within the Scope of ASC 810 Variable Interest Entity, Number of Policies Monitored, Not Within the Scope of ASC 810 Gross investment income Interest and Dividend Income, Operating Effects of Reinsurance [Line Items] Effects of Reinsurance [Line Items] 2051-2055 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, after Year 25 Through 30 Change in estimate for decreased conditional default rate ramp down period Recovery Estimate Sensitivity Analysis Change in Estimate for Decreased Conditional Default Rate Ramp Down Period Represents the change in expected loss on a pool of insured obligations that would result from a decrease in the conditional default rate ramp period. Par Outstanding Par Outstanding [Abstract] Par Outstanding Long-term Purchase Commitment, Category of Item Purchased [Domain] Long-Term Purchase Commitment, Category of Item Purchased [Domain] Individual: Individual [Axis] Income Tax Authority [Domain] Income Tax Jurisdiction [Domain] Dividends paid Payments of Ordinary Dividends, Common Stock Entities [Table] Entities [Table] Gross Schedule of Insured Financial Obligations with Credit Deterioration, Net Claim Liability 2051-2055 Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed More than 24 and Within 29 Years from Balance Sheet Date Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed More than 24 and Within 29 Years from Balance Sheet Date Issuance of a loan Payments to Fund Policy Loans 2026 (July 1 - September 30) Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, Third Quarter Annuity Reinsurance Insurance Disclosure [Text Block] Net fair value gains and losses on FG VIEs are expected to reverse to zero at maturity of the VIE debt Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Entity Interactive Data Current Entity Interactive Data Current Financial Guarantee Insurance Premiums [Table] Financial Guarantee Insurance Premiums [Table] Financial Guarantee Insurance Premiums [Table] Short-term investments with original maturities of over three months: Short-Term Investments [Abstract] Home Equity Line of Credit Home Equity Line of Credit [Member] Beginning of year Ending balance Premiums receivable, net of commissions payable Financial Guarantee Insurance Contracts, Premium Receivable Net Insured financial obligations insured contractual payments outstanding, net Insured Financial Obligations Insured Contractual Payments Outstanding, Net Represents the amount of insured contractual payments (principal and interest) outstanding on the underlying insured obligations for financial guaranty contracts, net of ceded contracts. Thames Water Utilities Finance PLC Thames Water Utilities Finance PLC [Member] Thames Water Utilities Finance PLC Liquidity Bonds Liquidity Bonds [Member] Liquidity Bonds Plaintiff, total board members Loss Contingency, Plaintiff, Total Board Members Loss Contingency, Plaintiff, Total Board Members Fixed-maturity securities, trading, measurement input Debt Securities, Trading, Measurement Input FG insurance premiums receivable FG insurance premiums receivable Financial Guarantee Insurance Contracts, Premium Receivable, Excluding Other Non Financial Guarantee Financial Guarantee Insurance Contracts, Premium Receivable, Excluding Other Non Financial Guarantee BIG Net Par Outstanding and Number of Risks Financial Guarantee Insurance Contracts, Claim Liability [Table Text Block] Entity Central Index Key Entity Central Index Key PEO Name PEO Name Total revenues Revenues Revenues Probability of paying more claims than being reimbursed (as a percent) Insured Financial Obligations, Aggregate Probability Weight of Possible Losses, Percentage Aggregate probability weight of possible losses, on a present value basis, for below-investment grade exposures. Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Carrying amount and estimated fair value financial instruments Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Cross-currency swaps Currency Swap [Member] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Income Taxes [Table] Income Taxes [Table] Income Taxes [Table] Fair value at start of period Fair value at end of period Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Premiums receivable, allowance for credit loss Premium Receivable, Allowance for Credit Loss Fair Value of Credit Derivatives and Effect of AGC and AGM Credit Spreads Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Exercise Price Award Exercise Price Number of delinquent payments Number of Delinquent Payments Number of Delinquent Payments Other invested assets fair value Other Investments Fair Value Disclosure This element represents the fair value investments categorized as other which are not in and of themselves material enough to require separate disclosure. Entity Filer Category Entity Filer Category Class of Stock [Domain] Class of Stock [Domain] Assured Life Re Acquisition, January 21, 2026 Policyholder Account Balance, Acquired Policyholder Account Balance, Acquired Corporate tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Schedule of Long-Lived Assets Held-for-sale [Table] Long-Lived Asset, Held-for-Sale [Table] Subsequent Event Type [Axis] Subsequent Event Type [Axis] FG VIEs’ Assets Variable Interest Entity, Assets [Member] Represents the consolidated variable interest entity's assets included in the reporting entity's statement of financial position at fair value. Reclassification from accumulated other comprehensive income, current period, before tax Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax Least Stressful Environment Least Stressful Environment [Member] Least Stressful Environment [Member] Multi-year Guaranteed Annuity Policyholder Balances Multi-year Guaranteed Annuity Policyholder Balances [Member] Multi-year Guaranteed Annuity Policyholder Balances Assured Guaranty Re Ltd. Assured Guaranty Re Ltd. [Member] Represents principal insurance company subsidiary, Assured Guaranty Re Ltd. ("AG Re"). Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Unpaid principal for FG VIEs’ liabilities with recourse Fair Value, Option, Liabilities with Recourse, Unpaid Principal Balance Fair Value, Option, Liabilities with Recourse, Unpaid Principal Balance Total expenses Expenses Segment expenses Benefits, Losses and Expenses Entity Address, Address Line One Entity Address, Address Line One 2026 (April 1 - June 30) Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Second Quarter Annuity Reinsurance Segment Annuity Reinsurance Segment [Member] Annuity Reinsurance Segment Accumulated Other Comprehensive Income (Loss) Total AOCI AOCI Attributable to Parent [Member] Investments [Domain] Investments [Domain] Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Table] Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Table] Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Table] Internal Credit Assessment [Axis] Internal Credit Assessment [Axis] Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract] Fair value gains (losses) on consolidated investment vehicles Fair Value, Gain (Loss) On Consolidated Investment Vehicles Fair Value, Gain (Loss) On Consolidated Investment Vehicles Internal Credit Assessment [Domain] Internal Credit Assessment [Domain] Derivatives Derivative Instruments and Hedging Activities Disclosure [Text Block] Statutory amount available for dividend payments without regulatory approval Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items] Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items] [Line Items] for Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Table] Fair Value as of Grant Date Award Grant Date Fair Value Weighted-average current discount rate Liability for Future Policy Benefit, Current Weighted-Average Discount Rate Employee compensation and benefit expenses Employee Benefits and Share-Based Compensation Policyholder Account Balance, Guaranteed Minimum Crediting Rate Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Table Text Block] Restricted stock awards (in shares) Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements Expected losses to be paid (recovered) Schedule of Insured Financial Obligations with Credit Deterioration, Net Claim Liability [Abstract] Document Quarterly Report Document Quarterly Report Fair Value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months Total Liability for Unpaid Claims and Claims Adjustment Expense, Net of Reinsurance and Salvage, Subrogation and Other Recoveries Liability for Unpaid Claims and Claims Adjustment Expense, Net of Reinsurance and Salvage, Subrogation and Other Recoveries Schedule of Quantitative Information About Level 3 Liabilities, Fair Value Measurements Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Second Lien Second Mortgage [Member] Counterparty Name [Domain] Counterparty Name [Domain] Plaintiff, terminated board members suing for reinstatement Loss Contingency, Plaintiff, Terminated Board Members Suing For Reinstatement Loss Contingency, Plaintiff, Terminated Board Members Suing For Reinstatement Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Accrued investment income Accrued Investment Income Receivable Investment Type [Axis] Investment Type [Axis] Total investments Investments Title Trading Arrangement, Individual Title Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Additions (reductions) for securities for which credit losses were previously recognized Debt Securities, Available-for-Sale, Excluding Accrued Interest, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal) Payments to acquire businesses, gross Payments to Acquire Businesses, Gross Premiums Receivable Premiums Receivable [Member] Non-PEO NEO Non-PEO NEO [Member] 2031-2035 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year 5 Through 10 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year 5 Through 10 Net Insured Financial Obligations, Outstanding Principal Amount, Net Represents the outstanding principal amounts of the underlying insured obligations for financial guaranty contracts, after netting out ceded contracts. Net paydowns of financial guaranty variable interest entities’ liabilities Paydown of Financial Guaranty Variable Interest Entities Liabilities Payments to reduce the outstanding balance of consolidated variable interest entities recourse and non-recourse liabilities. The Company consolidated these variable interest entities as the result of its control rights obtained under financial guaranty insurance contracts. Gross Unrealized Gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax All Award Types Award Type [Domain] Non-redeemable noncontrolling interest (Note 10) Equity, Attributable to Noncontrolling Interest Equity Awards Adjustments Equity Awards Adjustments [Member] Investments with no credit impairment, tax Other Comprehensive Income (Loss), Available-for-sale Securities, Without Credit Impairment, Tax Other Comprehensive Income (Loss), Available-for-sale Securities, Without Credit Impairment, Tax Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Other income (loss) Other Income Compensation Amount Outstanding Recovery Compensation Amount 2028 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year Three Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year Three Fair value of credit derivatives before effect of AG credit spread Credit Risk Derivatives at Fair Value before Effect of Credit Spread Net Fair value before effect of credit spread as of the balance sheet date of credit risk derivative assets, net of credit risk derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized on the balance sheet. Total BIG Total Noninvestment Grade [Member] Total Noninvestment Grade Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Estimated Fair Value Estimate of Fair Value Measurement [Member] Ending balance at original discount rate Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change 2046-2050 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, after Year 20 Through 25 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, after Year 20 Through 25 Schedule Of Net Expected Losses To Be Paid (Recovered) And Net Economic Development (Benefit) Loss Schedule Of Net Expected Losses To Be Paid (Recovered) And Net Economic Development (Benefit) Loss [Table Text Block] Schedule Of Net Expected Losses To Be Paid (Recovered) And Net Economic Development (Benefit) Loss [Table Text Block] Schedule of Investments [Line Items] Schedule of Investments [Line Items] Contracts Accounted for as Financial Guaranty Insurance Financial Guaranty Insurance [Text Block] Financial Guaranty Insurance [Text Block] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Receipt of fixed-maturity securities, available-for-sale Noncash or Part Noncash Acquisition, Investments Acquired, Available-for-sale Noncash or Part Noncash Acquisition, Investments Acquired, Available-for-sale Revenues Revenues [Abstract] Financial Guarantee Insurance And Other Product Line Financial Guarantee Insurance And Other Product Line [Member] Financial Guarantee Insurance And Other Product Line [Member] Total Schedule of Insured Financial Obligations with Credit Deterioration, Net Claim Liability, Undiscounted, Direct Assumed, Net Schedule of Insured Financial Obligations with Credit Deterioration, Net Claim Liability, Undiscounted, Direct Assumed, Net Liability for Future Policy Benefit, Activity Liability for Future Policy Benefit, Activity [Table Text Block] Number of securities Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions Accumulated other comprehensive income (loss), net of tax of $(62) and $(39) Accumulated Other Comprehensive Income (Loss), Net of Tax Net Exposure Specialty Business, Net Par Specialty Business, Net Par 2036-2040 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year 10 Through 15 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year 10 Through 15 2036-2040 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, after Year 10 Through 15 Financial Instruments [Domain] Financial Instruments [Domain] One-year CDS spread Credit Risk Contract, 1 Year Spread [Member] Credit Risk Contract, 1 Year Spread [Member] Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases BERMUDA BERMUDA Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Other comprehensive income (loss) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss) Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items] Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Line Items] Net Investment Income [Line Items] Net Investment Income [Line Items] Minimum Minimum [Member] Puerto Rico Defaulted Exposures Subject to a Plan Support Agreement Puerto Rico Defaulted Exposures Subject to a Plan Support Agreement [Member] Puerto Rico Defaulted Exposures Subject to a Plan Support Agreement Company Selected Measure Name Company Selected Measure Name Fair Value Measurement [Domain] Fair Value Measurement [Domain] Pro forma income (loss), after tax Business Combination, Pro Forma Information, Pro Forma Income (Loss), after Tax Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Net Change in Fair Value of Credit Derivatives Schedule of Credit Derivative Instruments, Net Change in Fair Value [Table Text Block] Schedule of Credit Derivative Instruments, Net Change in Fair Value [Table Text Block] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Distributed and undistributed income (loss) available to common shareholders of AGL and subsidiaries, diluted Net Income (Loss) Available to Common Stockholders, Diluted Change in Discount Rates on the LFPB AOCI, Liability for Future Policy Benefit, Parent [Member] 2030 Financial Guarantee Insurance Contracts, Future Expected, Net Loss to be Expensed in Fourth Full Fiscal Year For financial guarantee insurance contracts, the amount of net loss expected to be expensed within the fourth full fiscal year following the date of the latest balance sheet presented in the financial statements. Terminal growth rate Measurement Input, Long-Term Revenue Growth Rate [Member] 2027 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year Two Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year Two Financial Guarantee Insurance Premiums [Line Items] Financial Guarantee Insurance Premiums [Line Items] [Line Items] for Financial Guarantee Insurance Premiums [Table] BIG 2 Internal Noninvestment Grade, Level 2 [Member] Represents the below investment grade transactions for which lifetime losses are expected but for which no claims (other than liquidity claims) have yet been paid. Other credit derivative transactions which LBIE owes to AG Financial Products as per calculation of AG financial products Gain Contingency, Allegations, Payment For Termination of Other Credit Derivative Transactions Owed by Plaintiff to Defendant As Per Calculation of Defendant Gain Contingency, Allegations, Payment For Termination of Other Credit Derivative Transactions Owed by Plaintiff to Defendant As Per Calculation of Defendant Contingencies Commitments and Contingencies Disclosure [Text Block] Credit derivative liabilities, net Credit derivative liabilities, net Derivative Assets (Liabilities), at Fair Value, Net Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward] Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward] Diluted shares (in shares) Weighted Average Number of Shares Outstanding, Diluted Policyholder account balances for annuity reinsurance contracts Business Combination, Recognized Liability Assumed, Policyholder Account Balances Business Combination, Recognized Liability Assumed, Policyholder Account Balances Assured Life Re Acquisition, Multi-year Guaranteed Annuities Assured Life Re Acquisition, Multi-year Guaranteed Annuities [Member] Assured Life Re Acquisition, Multi-year Guaranteed Annuities Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Liability for Future Policy Benefit, Activity [Line Items] Liability for Future Policy Benefit, Activity [Line Items] Salvage and subrogation recoverable, net Financial Guarantee Insurance Contracts, Salvage and Subrogation Recoveries, Net Financial Guarantee Insurance Contracts, Salvage and Subrogation Recoveries, Net Total Schedule of Insured Financial Obligations with Credit Deterioration Insured Contractual Payments Outstanding Interest Net This element represents the amount of insured contractual payments outstanding attributable to interest accrued on the underlying insured obligations for financial guaranty insurance contracts presented in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guaranty insurance contracts, before adjusting for the effect of consolidating VIEs. Entity Small Business Entity Small Business Voting equity interest acquired, percentage Business Combination, Voting Equity Interest Acquired, Percentage Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Other operating expenses Other Cost and Expense, Operating Document Transition Report Document Transition Report Financial guaranty variable interest entities' liabilities, without recourse Variable Interest Entity, Consolidated, Carrying Amount, Liabilities, Without Recourse Variable Interest Entity, Consolidated, Carrying Amount, Liabilities, Without Recourse Schedule of Financial Instruments Not Carried at Fair Value Fair Value Disclosure of Asset and Liability Not Measured at Fair Value [Table Text Block] FG VIEs’ liabilities with recourse Fair Value, Option, Loans Held as Liabilities, Aggregate Difference, With Recourse Fair Value, Option, Loans Held as Liabilities, Aggregate Difference, With Recourse Underlying Securities Award Underlying Securities Amount Other comprehensive income (loss) before reclassifications Other Comprehensive Income (Loss), before Reclassifications, before Tax Maximum loss exposure Variable Interest Entity, Primary Beneficiary, Maximum Loss Exposure, Amount Gross realized gains on sales of available-for-sale securities Debt Securities, Available-for-Sale, Realized Gain Less: Specialty insurance premium receivable Specialty insurance premium receivable Financial Guarantee Insurance Contracts, Premium Receivable, Specialty Insurance Financial Guarantee Insurance Contracts, Premium Receivable, Specialty Insurance Equity Component [Domain] Equity Component [Domain] Document Period End Date Document Period End Date Number of custodial trusts Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Number of Custodial Trusts Represents the number of custodial trusts with whom the entity entered into put agreements. Foreign exchange remeasurement Liability for Future Policy Benefit, Foreign Exchange Remeasurement Liability for Future Policy Benefit, Foreign Exchange Remeasurement Non-credit impairment-related fair value gains (losses) on credit derivatives Non-credit Impairment-related Unrealized Fair Value Gains (Losses) on Credit Derivatives [Member] Non-credit Impairment-related Unrealized Fair Value Gains (Losses) on Credit Derivatives Income Taxes Income Tax Disclosure [Text Block] Accretion of discount Guarantor Obligations, Net Expected Loss Development After Recoveries for Representations and Warranties, Accretion Of Discount Guarantor Obligations, Net Expected Loss Development After Recoveries for Representations and Warranties, Accretion Of Discount Benefit expense for annuity reinsurance contracts Interest accrual Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Loan Category [Axis] SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Loan Category [Axis] United Kingdom UNITED KINGDOM Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Schedule of Investments [Table] Schedule of Investments [Table] Income Approach Valuation, Income Approach [Member] Inflation swaps Inflation Swap [Member] Inflation Swap 2026 (October 1 - December 31) Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed During Fourth Quarter Following Balance Sheet Date Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed During Fourth Quarter Following Balance Sheet Date Total shareholders’ equity Beginning balance Ending balance Equity, Including Portion Attributable to Noncontrolling Interest Average price paid per share (in dollars per share) Shares Acquired, Average Cost Per Share First Lien First Mortgage [Member] Document Type Document Type Level 3 Fair Value, Inputs, Level 3 [Member] Earnings Per Share Earnings Per Share [Text Block] Name Outstanding Recovery, Individual Name Loss Contingencies [Table] Loss Contingencies [Table] Number of businesses reinsured Reinsurance, Number Of Businesses Reinsured Reinsurance, Number Of Businesses Reinsured Insurance Product Line [Axis] Product and Service [Axis] Total Schedule of Insured Financial Obligations with Credit Deterioration, Gross Claim Liability, Net of Reinsurance Schedule of Insured Financial Obligations with Credit Deterioration, Gross Claim Liability, Net of Reinsurance 2036-2040 Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, after Year 10 Through 15 Litigation Status [Domain] Litigation Status [Domain] Number of contracts Annuity Reinsurance Agreement, Number Of Contracts Annuity Reinsurance Agreement, Number Of Contracts Measurement Input, Yield Measurement Input, Yield [Member] Measurement Input, Yield Asset management expenses Asset Management Expense Asset Management Expense Diversified real estate Diversified Real Estate [Member] Diversified Real Estate Investment Income [Table] Investment Income [Table] Total net outstanding exposure Schedule of Insured Financial Obligations with Credit Deterioration, Insured Contractual Payments Outstanding [Abstract] Statistical Measurement [Axis] Statistical Measurement [Axis] Realized gains (losses) on investments Gain (Loss) on Investments [Member] Effect of changes in cash flow assumptions Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change After 2055 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year 30 Through 35 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year 30 Through 35 Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Consolidated Investment Vehicles Consolidated Investment Vehicles [Member] Consolidated Investment Vehicles [Member] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Disposal Group Name [Axis] Disposal Group Name [Axis] Tax effect Income Tax Expense (Benefit) [Member] Income Tax Expense (Benefit) Payments related to tax withholding for share-based compensation Payment, Tax Withholding, Share-Based Payment Arrangement FRANCE FRANCE Number of entities Variable Interest Entity, Number of Entities Variable Interest Entity, Number of Entities Public finance Public Finance [Member] Represents obligations of diverse borrowers including governments and authorities providing such essential services as hospitals, schools, utilities and airports, each of which has unique credit characteristics. Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Due after one year through five years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value Derivative [Abstract] Distributed and undistributed income (loss) available to common shareholders of AGL and subsidiaries, basic Distributed and undistributed income (loss) available to common shareholders of AGL and subsidiaries, basic Net Income (Loss) Available to Common Stockholders, Basic Gross Schedule of Insured Financial Obligations with Credit Deterioration, Insured Contractual Payments Outstanding, Interest Entity Information [Line Items] Entity Information [Line Items] Future Equity Investments Future Equity Investments [Member] Future Equity Investments [Member] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Other liabilities. fair value disclosure Other Liabilities, Fair Value Disclosure Number of policies monitored Variable Interest Entity, Number of Policies Monitored Variable Interest Entity, Non-Consolidated, Number of Policies Monitored Level 1 Fair Value, Inputs, Level 1 [Member] Beginning balance (in shares) Ending balance (in shares) Shares, Outstanding Total Schedule of Insured Financial Obligations with Credit Deterioration, Statement of Financial Position, Unearned Premium Revenue, Net of Reinsurance Recoverable Schedule of Insured Financial Obligations with Credit Deterioration, Statement of Financial Position, Unearned Premium Revenue, Net of Reinsurance Recoverable Gross premiums received, net of commissions Financial Guarantee Insurance Contracts, Premium Receivable, Proceeds from Premiums Received Diluted (in dollars per share) Diluted EPS (in dollars per share) Earnings Per Share, Diluted Net Expected Loss to be Expensed Insurance Contracts Financial Guaranty Insurance Contracts, Expected Future Recognition of Premiums and Losses [Table Text Block] Tabular disclosure of the expected timing of the recognition in earnings of financial guaranty insurance net deferred premium revenue and present value of net expected losses to be expensed, pre-tax. Supplemental disclosure of non-cash activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] % of total net par outstanding Insured Financial Obligations, Outstanding Principle Amount, Percentage Represents the net outstanding principal amounts of the underlying insured obligations for each category of financial guaranty contracts, as a percentage of the total outstanding principal amount within the identified asset class. Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Net Expected Loss to be Paid (Recovered) Net expected loss to be paid (recovered), beginning of period Net expected loss to be paid (recovered), end of period Net expected loss to be paid (recovered) - FG insurance Guarantor Obligations, Net Expected Loss to be Paid After Recoveries for Representations and Warranties Guarantor Obligations, Net Expected Loss to be Paid After Recoveries for Representations and Warranties 2036-2040 Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed More than 9 and within 14 Years from Balance Sheet Date Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed More than 9 and within 14 Years from Balance Sheet Date Consolidation Items [Domain] Consolidation Items [Domain] Investments, Debt and Equity Securities [Abstract] Investments, Debt and Equity Securities [Abstract] Assured Life Re Acquisition Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Acquired Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Acquired CDS Spread on AGC and AGM Schedule of Credit Spread Effect on Credit Derivatives, Fair Value [Table Text Block] Tabular disclosure of the effect of the entity's credit spread on the fair value of credit derivatives. Common shares repurchases Stock Repurchased and Retired During Period, Value Income Taxes [Line Items] Income Taxes [Line Items] [Line Items] for Income Taxes [Table] Range of discount rates Guarantor Obligations, Net Expected Loss to be Paid After Recoveries for Representations and Warranties, Discount Rate Guarantor Obligations, Net Expected Loss to be Paid After Recoveries for Representations and Warranties, Discount Rate Net income (loss) Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Earnings Credit Derivatives Subordination and Ratings and Net Par Outstanding by Internal Rating Disclosure of Credit Derivatives [Table Text Block] BIG 3 Internal Noninvestment Grade, Level 3 [Member] Represents the below investment grade transactions for which lifetime losses are expected and on which claims (other than liquidity claims) have been paid. Transactions remain in this category when claims have been paid and only recoverable remains. Change in instrument-specific credit risk on financial guaranty variable interest entities’ liabilities with recourse, net of tax provision (benefit) Other Comprehensive Income (Loss), Financial Liability, Fair Value Option, after Tax and Reclassification Adjustment Change in net unrealized gains (losses) on investments OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Due after five years through 10 years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value Distributions Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Investments Business Combination, Recognized Asset Acquired, Investments Business Combination, Recognized Asset Acquired, Investments Intersegment Eliminations Intersegment Eliminations [Member] Fixed-Maturity Securities Gross Unrealized Loss by Length of Time Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value [Table Text Block] Outstanding Exposure Outstanding Exposure [Text Block] The entity's insurance policies and credit derivative contracts guarantee the scheduled payments of principal and interest ("Debt Service") on public finance and structured finance obligations. Outstanding Exposure includes outstanding par and/or debt service amounts, including outstanding exposures on VIE's whether or not they are consolidated under US GAAP, on credits that are guaranteed by the entity. Expiration Date Trading Arrangement Expiration Date Other Commitments [Domain] Other Commitments [Domain] Recourse Status [Axis] Recourse Status [Axis] Shareholders’ equity Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Non-U.S. government securities Debt Security, Government, Non-US [Member] Other Other Investments [Member] Benefit payments Policyholder Account Balance, Benefit Payment 2030 Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, Year Five Long-Lived Assets Held-for-sale [Line Items] Long-Lived Assets Held-for-Sale [Line Items] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Investments Investment in Debt and Equity Instruments and Cash and Cash Equivalent [Text Block] Gain Contingencies, Nature [Axis] Gain Contingencies, Nature [Axis] After 2055 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, after Year 30 Through 35 Entity Current Reporting Status Entity Current Reporting Status Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Total Schedule of Insured Financial Obligations with Credit Deterioration Insured Contractual Payments Outstanding Net This element represents the amount of insured contractual payments outstanding on the underlying insured obligations for financial guaranty insurance contracts presented in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guaranty insurance contracts, before adjusting for the effect of consolidating VIEs. Consolidated Entities [Domain] Consolidated Entities [Domain] 4.00% - 5.00% Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 to 0499 [Member] Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0400 to 0499 Pension Risk Transfers Insurance Liabilities Pension Risk Transfers Insurance Liabilities [Member] Pension Risk Transfers Insurance Liabilities Financial Instrument [Axis] Financial Instrument [Axis] Expenses Benefits, Losses and Expenses [Abstract] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Executive Category: Executive Category [Axis] Gross Unrealized Loss Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss AOCI Including Portion Attributable to Noncontrolling Interest [Abstract] AOCI Including Portion Attributable to Noncontrolling Interest [Abstract] Weighted-average original discount rate Liability for Future Policy Benefit, Original Weighted-Average Discount Rate Liability for Future Policy Benefit, Original Weighted-Average Discount Rate Market Approach Valuation, Market Approach [Member] Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] Current Fiscal Year End Date Current Fiscal Year End Date Net economic loss development (benefit) Total economic loss development (benefit) RMBS losses Guarantor Obligations, Net Expected Loss Development After Recoveries for Representations and Warranties Guarantor Obligations, Net Expected Loss Development After Recoveries for Representations and Warranties Gross Unrealized Loss Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 2028 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Year Three Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Gross Unrealized Loss Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss Net assets Business Combination, Recognized Asset Acquired to Liability Assumed, Excess (Less) Potentially dilutive securities excluded from computation of EPS because of antidilutive effect (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Assured Guaranty US Holdings Inc. 3.600% Senior Notes due 2051 (and the related guarantee of Registrant) Assured Guaranty US Holdings Inc. 3.600% Senior Notes due 2051 [Member] Assured Guaranty US Holdings Inc. 3.600% Senior Notes due 2051 Interest Schedule of Insured Financial Obligations with Credit Deterioration, Insured Contractual Payments Interest [Abstract] -- None. No documentation exists for this element. -- 2046-2050 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, after Year 20 Through 25 Net cash flows provided by (used in) financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Measure: Measure [Axis] Puerto Rico PUERTO RICO Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Net Fair Value Asset (Liability) Derivative, Fair Value, Net Cash surrender value Policyholder Account Balance, Cash Surrender Value Number of active proceedings Number Of Active Proceedings Number Of Active Proceedings Alternative Investments, Authorized Amount To Invest Alternative Investments, Authorized Amount To Invest Alternative Investments, Authorized Amount To Invest Statutory amount available for dividend payments, deficit Statutory Accounting Practices, Statutory Amount Available for Dividend Payments, Deficit Statutory Accounting Practices, Statutory Amount Available for Dividend Payments, Deficit Pension Risk Transfers Variable Interest Entities Pension Risk Transfers Variable Interest Entities [Member] Pension Risk Transfers Variable Interest Entities Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Due after 10 years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Investment expenses Investment Income, Investment Expense Entity Tax Identification Number Entity Tax Identification Number Discounted Cash Flow Valuation Technique, Discounted Cash Flow [Member] SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Loan Type [Axis] SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Loan Type [Axis] Schedule of Consolidated FG VIE's Schedule of Variable Interest Entities [Table Text Block] Hedge cost (in basis points) (bps) Hedge Cost [Member] Hedge Cost Common stock, shares issued (in shares) Common Stock, Shares, Issued Cash and cash equivalents of financial guaranty variable interest entities Cash Of Financial Guaranty Variable Interest Entities Cash Of Financial Guaranty Variable Interest Entities Change in the allowance for credit losses and intent to sell Debt Securities, Available-for-Sale, Excluding Accrued Interest, Allowance for Credit Loss, Period Increase (Decrease) CMBS Commercial Mortgage-Backed Securities [Member] Other assets Business Combination, Recognized Asset Acquired, Other Asset Business Combination, Recognized Asset Acquired, Other Asset U.S. Transportation U.S. Transportation [Member] U.S. Transportation Accretion of discount on net premiums receivable Financial Guarantee Insurance Contracts, Net Premiums Receivable Adjustment Accretion of Discount on Net Premium Receivable This element represents the accretion of the discount for premiums receivable, net of ceded contracts, on financial guaranty insurance contracts. Trading Arrangement: Trading Arrangement [Axis] Total Shareholder Return Amount Total Shareholder Return Amount Commitments and Contingencies Legal Proceedings Loss Contingencies [Line Items] Net income (loss) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings FG VIEs’ assets Fair Value, Option, Aggregate Differences, Loans and Long-Term Receivables Corporate division Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Security Exchange Name Security Exchange Name Exit multiple-price to earnings Measurement Input, Exit Multiple, Price To Earnings [Member] Measurement Input, Exit Multiple, Price To Earnings Effect of actual variances from expected experience Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience 2031-2035 Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, after Year 5 Through 10 Shares repurchased (in shares) Stock Repurchased During Period, Shares Financial Guaranty Insurance BIG Transaction Loss Summary Financial Guarantee Insurance Contracts, Claim Liability [Line Items] Credit Credit [Member] After 2055 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, after Year 30 Through 35 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, after Year 30 Through 35 Asset Class [Domain] Asset Class [Domain] Asset Class [Domain] Maturities and paydowns of fixed-maturity securities, trading Proceeds from Maturity, Repayment, and Call, Debt Security, Trading, Held-for-Investment Net income (loss) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Potential recoveries Schedule of Insured Financial Obligations with Credit Deterioration, Reductions of Gross Claim Liability, Gross Potential Recoveries [Abstract] -- None. No documentation exists for this element. -- Statement [Line Items] Statement [Line Items] Schedule of Share Repurchases Schedule Of Share Repurchases [Table Text Block] Schedule Of Share Repurchases [Table Text Block] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Loss and LAE Reserve paid Insured Financial Obligations, Liability for Unpaid Claims Adjustment Expense, Claims Paid Insured Financial Obligations, Liability for Unpaid Claims Adjustment Expense, Claims Paid Common Stock Common Stock [Member] Adjustments: Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment [Abstract] Increase (decrease) in cash and cash equivalents and restricted cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Conditional prepayment rate (CPR) Measurement Input, Prepayment Rate [Member] Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] Statistical Measurement [Domain] Statistical Measurement [Domain] Underlying Asset Class [Axis] Underlying Asset Class [Axis] Amortized cost Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, before Allowance for Credit Loss Settled Litigation Settled Litigation [Member] Decrease in the plateau period used to calculate potential change in loss estimate (in months) Guarantor Obligations, Projected Loss Assumptions, Conditional Default Rate, Plateau Rate, Projection Period Decrease Represents the decrease in the conditional default rate plateau period for which the change in loss estimate for a pool of insured obligations is calculated. Number of risks, financial guaranty insurance Total (in contracts) Schedule of Insured Financial Obligations with Credit Deterioration, Number of Contracts Issued and Outstanding Benefit payments Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment Financial Guarantee Policies Paid in Installments Financial Guarantee Policies Paid in Installments [Member] Represents financial guarantee insurance contracts paid in installments. Asset Class [Axis] Asset Class [Axis] Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Positive Outcome of Litigation Positive Outcome of Litigation [Member] Interest rate swaps Interest Rate Swap [Member] Other comprehensive income (loss) Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) Global minimum tax, benefit Effective Income Tax Rate Reconciliation, Global Minimum Tax, Amount Effective Income Tax Rate Reconciliation, Global Minimum Tax, Amount Equity in Earnings (Losses) of Investees Segment equity in earnings (losses) of investees Income (Loss) from Equity Method Investments Unearned premium reserve Unearned Premiums Basic Earnings Per Share (EPS): Earnings Per Share, Basic [Abstract] Number of surveillance categories Number Of Surveillance Categories Number Of Surveillance Categories Projected loss assumptions, period of consistent conditional default rate Guarantor Obligations, Projected Loss Assumptions, Period Of Consistent Conditional Default Rate Guarantor Obligations, Projected Loss Assumptions, Period Of Consistent Conditional Default Rate Subtotal 2026 Financial Guarantee Insurance Contracts, Future Expected Premium Revenue to be Recognized, Net, Fiscal Year Financial Guarantee Insurance Contracts, Future Expected Premium Revenue to be Recognized, Net, Fiscal Year Gross Schedule of Insured Financial Obligations with Credit Deterioration, Statement of Financial Position, Claim Liability Pledged Status [Axis] Pledged Status [Axis] Gross Unrealized Losses Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] FG insurance net earned premiums Financial Guarantee Insurance Contracts, Premiums Earned, Net Financial Guarantee Insurance Contracts, Premiums Earned, Net Basic (in dollars per share) Basic EPS (in dollars per share) Earnings Per Share, Basic Less: Amounts reclassified from AOCI to: Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax [Abstract] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Liabilities: Liabilities, Fair Value Disclosure [Abstract] Dividend payment restrictions schedule amount of statutory capital Dividend Payment Restrictions Schedule Amount of Statutory Capital The maximum amount of statutory capital that may be paid out as dividends without prior approval from a regulatory agency. Discount margin Measurement Input, Discount Rate [Member] Loans Insured Or Guarantee For Government Authorities [Domain] Loans Insured Or Guarantee For Government Authorities [Domain] [Domain] for Loans Insured Or Guarantee For Government Authorities [Axis] SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Loan Category [Domain] SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Loan Category [Domain] Other comprehensive income (loss) Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Schedule of Information by Operating Segments Schedule of Segment Reporting Information, by Segment [Table Text Block] Weighted-average liability duration (in years) (1) Liability for Future Policy Benefit, Weighted-Average Duration 2026 (April 1 - June 30) Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Second Quarter Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Second Quarter Measurement Input Type [Domain] Measurement Input Type [Domain] Fixed Maturity Securities and Short Term Investments by Security Type Schedule of Available-for-Sale Securities Reconciliation [Table Text Block] Affiliated Entity Affiliated Entity [Member] 2026 (April 1 - June 30) Financial Guarantee Insurance Contracts, Future Expected, Net Loss to be Expensed During Second Quarter Following Balance Sheet Date For financial guaranty insurance contracts, the amount of net loss expected to be expensed during the second quarter of the subsequent annual period following the statement of financial position reporting date. Change in unrealized gains/(losses) related to financial instruments held Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) Policy charges Policyholder Account Balance, Policy Charge Deferred Loan Recovery Scenario [Domain] Deferred Loan Recovery Scenario [Domain] Deferred Loan Recovery Scenario [Domain] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Category of Item Purchased [Axis] Category of Item Purchased [Axis] Reconciling Items [Domain] Reconciling Items [Domain] Reconciling Items [Domain] Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] No Credit Impairment AOCI, Gain (Loss), Debt Securities, Available-for-Sale, without Allowance for Credit Loss, Parent [Member] Rollforward of Credit Losses for Available-for-sale Fixed-Maturity Securities Debt Securities, Available-for-Sale, Allowance for Credit Loss [Table Text Block] Gross Schedule of Insured Financial Obligations with Credit Deterioration, Insured Contractual Payments Outstanding Total liabilities and shareholders’ equity Liabilities and Equity 2027 Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, Year Two Deferred acquisition costs Deferred Policy Acquisition Cost 2041-2045 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, after Year 15 Through 20 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, after Year 15 Through 20 Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] Asset management revenues Insurance Agency Management Fee Other liabilities Business Combination, Recognized Liability Assumed, Other Liability Business Combination, Recognized Liability Assumed, Other Liability Schedule of Credit Derivatives [Table] Credit Derivative [Table] Subtotal Schedule of Insured Financial Obligations with Credit Deterioration Gross Claim Liability Subtotal [Abstract] -- None. No documentation exists for this element. -- Gross Schedule of Insured Financial Obligations with Credit Deterioration, Gross Claim Liability After 2055 Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed Beyond Twenty-Ninth Fiscal Year from Balance Sheet Date Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed Beyond Twenty-Ninth Fiscal Year from Balance Sheet Date Percentage of CDS contracts fair valued using minimum premium Percentage of CDS Contracts Fair Valued Using Minimum Premium Percentage of CDS Contracts Fair Valued Using Minimum Premium Concentration Risk Type [Domain] Concentration Risk Type [Domain] Purchases of and contributions to other invested assets Payments to Acquire Other Investments Pay vs Performance Disclosure [Line Items] SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Loan Type [Domain] SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Loan Type [Domain] U.K. Student Accommodations U.K. Student Accommodations [Member] U.K. Student Accommodations 2036-2040 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, after Year 10 Through 15 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, after Year 10 Through 15 Financial guaranty variable interest entities' liabilities, with recourse Variable Interest Entity, Consolidated, Carrying Amount, Liabilities, With Recourse Variable Interest Entity, Consolidated, Carrying Amount, Liabilities, With Recourse Effects of Reinsurance [Table] Effects of Reinsurance [Table] Assured Life Re Acquisition Business Combination [Text Block] 2026 (October 1 - December 31) Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Fourth Quarter Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Fourth Quarter 2046-2050 Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, after Year 20 Through 25 Fair value gains (losses) on trading securities still held Fair Value, Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss) 2029 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year Four Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year Four Trading Activity, by Type [Domain] Trading Activity, by Type [Domain] Fair Value Level 3 Rollforward Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Schedule of Variable Interest Entities [Table] Variable Interest Entity [Table] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Company Selected Measure Amount Company Selected Measure Amount Cash Cash Comprehensive income (loss) attributable to Assured Guaranty Ltd. Comprehensive Income (Loss), Net of Tax, Attributable to Parent Measurement Input Type [Axis] Measurement Input Type [Axis] Disposal Group Name [Domain] Disposal Group Name [Domain] Name Measure Name More Stressful Environment More Stressful Environment [Member] More Stressful Environment [Member] Residual value insurance policies exposure downgraded Gross Exposure Specialty Business, Gross Par Specialty Business, Gross Par Fair value gains (losses) of freestanding derivatives in the Annuity Reinsurance segment Fair Value Gains (Losses) Of Derivatives In Annuity Reinsurance Segment [Member] Fair Value Gains (Losses) Of Derivatives In Annuity Reinsurance Segment Fair Value, Liabilities Measured on Recurring Basis Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Maturities and paydowns Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-Sale Period of insured credit performance of guaranteed obligations (in some cases over) Insured Financial Obligations, Insured Credit Performance of Guaranteed Obligations, Term Insured Financial Obligations, Insured Credit Performance of Guaranteed Obligations, Term Total Financial Guarantee Insurance Contracts, Unearned Premium Revenue, Excluding Claims Paid Not Yet Expensed, Net Amount of unearned premium revenue in the statement of financial position for financial guaranty insurance contracts, net of the unexpired portion of premiums ceded and before adjustment for loss claims paid but not yet expensed. Other comprehensive income (loss) Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Gain (Loss) Included in Other Comprehensive Income (Loss) Distribution of Fixed Maturity Securities by Contractual Maturity Available-for-Sale Securities, Debt Maturities [Abstract] Long-term debt Long-term debt Long-Term Debt Legal Entity [Axis] Legal Entity [Axis] Total assets Assets Assets Foreign Currency Concentration Risk Foreign Currency Concentration Risk [Member] Foreign Currency Concentration Risk [Member] Number of holding companies with outstanding public debt Holding Companies with Outstanding Public Debt, Number Holding Companies with Outstanding Public Debt, Number AGL Subsidiaries Assured Guaranty Subsidiaries [Member] Assured Guaranty Subsidiaries [Member] Credit Derivatives Contract Type [Axis] Credit Derivatives Contract Type [Axis] Geographical [Domain] Geographical [Domain] Fair value gains (losses) on CCS Fair Value Gains (Losses) on Committed Capital Securities [Member] Fair Value Gains (Losses) on Committed Capital Securities Other Underlying, Other [Member] Other segment items Segment Reporting, Other Segment Item, Amount Total pre-tax realized and unrealized gains (losses) recorded in: Total Pretax Realized And Unrealized Gains (Losses) Recorded As Assets [Abstract] Total Pretax Realized And Unrealized Gains (Losses) Recorded As Assets [Abstract] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Deconsolidation Noncontrolling Interest, Decrease from Deconsolidation Assets: Assets, Fair Value Disclosure [Abstract] Due after one year through five years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Percent of deferred loan balances to be recovered Guarantor Obligations, Projected Loss Assumption, Deferred Loan Balances to be Recovered, Percent Guarantor Obligations, Projected Loss Assumption, Deferred Loan Balances to be Recovered, Percent Dividends per share (in dollars per share) Common Stock, Dividends, Per Share, Declared Other invested assets (includes $3 and $3, at fair value) Other invested assets Other Investments Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Risk free discount rate Insured Financial Obligations, Claim Liability, Risk Free Discount Rate Insured Financial Obligations, Claim Liability, Risk Free Discount Rate Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Total assets Business Combination, Recognized Asset Acquired, Asset Level 2 Fair Value, Inputs, Level 2 [Member] Schedule of Non-Financial Guaranty Exposure Schedule of Non-Financial Guaranty Exposure [Table Text Block] Schedule of Non-Financial Guaranty Exposure [Table Text Block] 2030 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Year Five Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Year Five Equity method investments Equity Method Investments BIG 1 Internal Noninvestment Grade, Level 1 [Member] Represents the below investment grade transactions showing sufficient deterioration to make lifetime losses possible, but for which none are currently expected. Transactions on which claims have been paid but are expected to be fully reimbursed (other than investment grade transactions on which only liquidity claims have been paid) are in this category. Investments with no credit impairment, net of tax provision (benefit) of $(16) and $6 Other Comprehensive Income (Loss), Available-For-Sale Securities, Without Credit Impairment, Net Of Tax Other Comprehensive Income (Loss), Available-For-Sale Securities, Without Credit Impairment, Net Of Tax Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Business Combination [Domain] Business Combination [Domain] Debt Service Outstanding Schedule of Insured Contractual Payments Outstanding [Table Text Block] Tabular disclosure of the outstanding amounts of the insured contractual payments (principal and interest) outstanding on the underlying the entity's financial guaranty contracts, prior to and net of cessions Asset Pledged as Collateral Asset Pledged as Collateral [Member] Credit derivative liabilities, net, measurement input Derivative Asset (Liability) Net, Measurement Input Funds Withheld Funds Withheld [Member] Funds Withheld Net Fair Value Asset (Liability) Net fair value of credit derivatives Credit Risk Derivatives, at Fair Value, Net PEO PEO [Member] Transfers into Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 Investments Classified by Contractual Maturity Date Investments Classified by Contractual Maturity Date [Table Text Block] Fixed-maturity securities, trading, at fair value Fixed-maturity securities, trading Debt Securities, Trading Gross (in years) Insured Financial Obligations with Credit Deterioration, Remaining Weighted Average Contract Period Income (loss) before income taxes and equity in earnings (losses) of investees Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Due within one year Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value 5.00% - 6.00% Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0500 to 0599 [Member] Policyholder Account Balance, Guaranteed Minimum Crediting Rate, Range from 0500 to 0599 United States UNITED STATES Gross Unrealized Loss by Length of Time Dept Security, Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] Dept Security, Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] Retained Earnings Retained Earnings [Member] Income Tax Authority [Axis] Income Tax Jurisdiction [Axis] A Internal Investment Grade, A [Member] The entity's internal risk assessment category, A, representing the fourth lowest risk level. 12 months or more Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer [Abstract] Cash and cash equivalents and restricted cash at beginning of period Cash and cash equivalents and restricted cash at end of period Cash and cash equivalents and restricted cash at end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Income Statement [Abstract] Income Statement [Abstract] Fair Value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer Investments, fair value disclosure Investments, Fair Value Disclosure Insurance Product Line [Domain] Product and Service [Domain] Future Premiums to be Collected [Abstract] Future Premiums to be Collected [Abstract] Future Premiums to be Collected Net investment income Net investment income Net Investment Income Total Parent [Member] Net income (loss) Net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Assets of CIVs - equity securities, measurement input Equity Securities, FV-NI, Measurement Input FG VIEs’ assets Assets, Fair Value Measurement Input Assets, Fair Value Measurement Input 2030 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year Five Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year Five Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Total liabilities carried at fair value FG VIEs' liabilities Liabilities, Fair Value Disclosure Business Combination [Table] Business Combination [Table] Notional Derivative, Notional Amount Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Policyholder Account Balance, Guaranteed Minimum Crediting Rate Range [Domain] Policyholder Account Balance, Guaranteed Minimum Crediting Rate Range [Domain] Subtotal Operating Segments And Corporate Non Segment [Member] Operating Segments And Corporate Non Segment Business Combination, Recognized Asset Acquired and Liability Assumed Business Combination, Recognized Asset Acquired and Liability Assumed [Table Text Block] 2026 (April 1 - June 30) Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, Second Quarter Period from plateau to intermediate conditional default rate (in months) Guarantor Obligations, Projected Loss Assumptions, Period to Reach Intermediate Conditional Default Rate Represents the period over which the conditional default rate on a pool of insured obligations is assumed to improve from the current level to an intermediate conditional default rate. City Area Code City Area Code Gross Premium Receivable Net of Ceding Commissions [Roll Forward] Financial Guarantee Insurance Contracts, Premium Receivable [Roll Forward] Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Liability for Future Policy Benefit Liability for Future Policy Benefit, Composition [Table Text Block] Liability for Future Policy Benefit, Composition ISCR on FG VIEs’ Liabilities with Recourse Accumulated Gain (Loss), Financial Liability, Fair Value Option, Attributable to Parent [Member] Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Base Scenario Base Scenario [Member] Represents the current or base level on the basis of which the sensitivity analysis is done. Cash flows from investing activities: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Remaining weighted average contract period Schedule of Insured Financial Obligations with Credit Deterioration, Remaining Weighted Average Contract Period [Abstract] -- None. No documentation exists for this element. -- Net realized investment gains (losses) Debt Securities, Realized Gain (Loss) Government agency obligations as a percentage of total mortgage backed securities Government Agency Obligations as a Percentage of Total Mortgage Backed Securities Represents government agency obligations as a percentage of the aggregate amortized cost of mortgage backed securities. FG VIEs’ assets, measurement input Equity Securities, FV-NI Other liabilities (includes $26 and $21, at fair value) Other liabilities Other Liabilities 2026 (October 1 - December 31) Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Fourth Quarter Total unrealized losses for securities having losses greater than 10% of book value for 12 months or more Available-for-sale Securities, Continuous Unrealized Loss Position Twelve Months or Longer Greater than 10 Percent Book Value, Aggregate Losses This item represents the excess of amortized cost basis over fair value of securities that have been in a loss position for twelve months or longer for those securities which are categorized neither as held-to-maturity nor trading securities and which have unrealized losses greater than 10% of book value. Non-U.S. public finance Non-US [Member] Plus: Effect of AG credit spread Derivative Credit Risk Valuation Adjustment, Derivative Liabilities 2029 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Year Four Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Year Four Realized and unrealized fair value gains (losses) of the embedded derivative in funds withheld Fair Value Gains (Losses) Of Embedded Derivatives In Funds Withheld [Member] Fair Value Gains (Losses) Of Embedded Derivatives In Funds Withheld Contingent Value Instruments Contingent Value Instruments [Member] Contingent Value Instruments 2031-2035 Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed More than Four and Within 9 Years from Balance Sheet Date Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed More than Four and Within 9 Years from Balance Sheet Date Business and Basis of Presentation Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Fair value at start of period Fair value at end of period Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis with Unobservable Inputs Other Other Assets and Other Invested Assets [Member] Other Assets and Other Invested Assets [Member] Other Performance Measure, Amount Other Performance Measure, Amount U.S. government and agencies US Treasury and Government [Member] Dividend payment restrictions schedule, percentage of statutory capital and surplus Dividend Payment Restrictions Schedule, Percentage of Statutory Capital and Surplus The maximum percentage of statutory capital and surplus that may be paid out as dividends without prior approval from a regulatory agency. Net Expected Loss to be Paid By Accounting Model Schedule of Net Expected Losses to be Paid [Table Text Block] Schedule of Net Expected Losses to be Paid [Table Text Block] Related Party [Domain] Related and Nonrelated Parties [Domain] Subtotal 2026 Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed During Fiscal Year Following Balance Sheet Date Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed During Fiscal Year Following Balance Sheet Date Litigation Status [Axis] Litigation Status [Axis] Derivative Instrument [Axis] Derivative Instrument [Axis] Fair Value Measurement Fair Value of Financial Instruments, Policy [Policy Text Block] Restricted cash (included in other assets) Restricted Cash Share-based compensation Stock Issued During Period, Value, Share-based Compensation and Other Includes share-based compensation expense, net share activity under the company's long-term incentive plan, employee stock purchase plan, excess tax benefits for share-based compensation and share cancellations in satisfaction of withholding tax requirements. Period after the end of the reporting period within which the ceded paid losses are typically settled (in days) Reinsurance Recoverables, Period after End of Reporting Period for Settlement of Ceded Paid Losses Represents the period after the end of the reporting period within which the ceded paid losses are settled. Total Financial Guarantee Insurance Contracts Future Expected Premium Revenue to be Recognized, Net Financial Guarantee Insurance Contracts Future Expected Premium Revenue to be Recognized, Net Assets of consolidated investment vehicles (includes $— and $167, at fair value) Assets of Consolidated Investment Vehicles Assets of Consolidated Investment Vehicles Investments: Investments [Abstract] Entity [Domain] Entity [Domain] Net cash flows provided by (used in) investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Schedule of Insured Financial Obligations [Table] Schedule of Insured Financial Obligations [Table] Schedule of Insured Financial Obligations [Table] Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Document Fiscal Year Focus Document Fiscal Year Focus Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Nonrecourse Nonrecourse [Member] Effective income tax rate reconciliation, percent Effective Income Tax Rate Reconciliation, Percent Debt Service Debt Service [Abstract] Debt Service Carrying Amount Reported Value Measurement [Member] Business Combination, Acquisition-Related Cost, Expense Business Combination, Acquisition-Related Cost, Expense Weighted-average risk-free rate used to discount premiums Financial Guarantee Insurance Contract, Premium Received over Contract Period, Premium Receivable, Weighted-Average Risk-Free Discount Rate Changes in the expected term and debt service assumptions Financial Guarantee Insurance Contracts, Premiums Receivable, Increase (Decrease), Change in Period of Contract Assured Life Re Acquisition, Pension Risk Transfers Assured Life Re Acquisition, Pension Risk Transfers [Member] Assured Life Re Acquisition, Pension Risk Transfers Number of risks Insured Financial Obligations, Number of Contracts Represents the number of unique credits in the insured portfolio. Equity [Abstract] Equity [Abstract] Financial Guarantee Insurance Product Line Financial Guarantee Insurance Product Line [Member] Yield (as a percent) Fair Value Inputs Yield Represents the yield used as an input to measure fair value. Selected Information for Policies Paid in Installments Financial Guarantee Insurance Contracts, Policies Paid in Installments [Table Text Block] Tabular disclosure of the selected information for financial guarantee insurance policies paid in installments, including premiums receivable, gross deferred premium revenue, weighted-average risk-free rate used to discount premiums and weighted-average period of premiums receivable. Other Comprehensive Income Location [Domain] Other Comprehensive Income Location [Domain] Derivatives Derivatives, Policy [Policy Text Block] Segment Information Segment Reporting Disclosure [Text Block] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Projected loss assumptions, period to reach final loss severity rate Guarantor Obligations, Projected Loss Assumptions, Period to Reach Final Loss Severity Rate Represents the period over which the conditional prepayment rate assumed for a pool of insured obligations trends from the initial to the final rate. Increase (Decrease) in Shareholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Weighted-average crediting rate Policyholder Account Balance, Weighted Average Crediting Rate Fair value inputs term Other Assets, Fair Value Disclosure, Measurement Input Other Assets, Fair Value Disclosure, Measurement Input Schedule of Expected Losses to be Paid [Line Items] Schedule of Expected Losses to be Paid [Line Items] [Line Items] for Schedule of Expected Losses to be Paid [Table] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Weighted Average Weighted Average [Member] Deferred Profit Liability Deferred Profit Liability [Member] Deferred Profit Liability Net Par Outstanding on Credit Derivatives Financial Guaranty Contracts Accounted for as Credit Derivatives Abstract Exchange [Domain] Exchange [Domain] Fixed-maturity securities, available for sale, measurement input Debt Securities, Available-for-Sale, Measurement Input Changes in Accumulated Other Comprehensive Income by Component Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] New business and supplemental premiums, net of commissions Financial Guarantee Insurance Contracts Premium Receivable New Business Written Changes in timing and assumptions Guarantor Obligations, Net Expected Loss Development After Recoveries for Representations and Warranties, Changes In Timing And Assumptions Guarantor Obligations, Net Expected Loss Development After Recoveries for Representations and Warranties, Changes In Timing And Assumptions Insurance reserve financing and securitizations Insurance Reserve Financing And Securitizations [Member] Insurance Reserve Financing And Securitizations Reserves (salvage) Schedule of Insured Financial Obligations with Credit Deterioration, Reserves Salvage [Abstract] -- None. No documentation exists for this element. -- RMBS Residential Mortgage-Backed Securities [Member] Arrangement Duration Trading Arrangement Duration Estimated remaining weighted average life of credit derivatives (in years) Average Term of Credit Risk Derivatives Acquiree's earnings (loss) since acquisition date, actual Business Combination, Acquiree's Earnings (Loss) since Acquisition Date, Actual Puerto Rico Electric Power Authority Puerto Rico Electric Power Authority [Member] Puerto Rico Electric Power Authority [Member] European Renewable Energy European Renewable Energy [Member] European Renewable Energy Segments [Axis] Segments [Axis] Loans Insured Or Guarantee For Government Authorities [Axis] Loans Insured Or Guarantee For Government Authorities [Axis] Loans Insured Or Guarantee For Government Authorities [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Commitment to Provide Guarantees Commitment to Provide Guarantees [Member] Commitment to Provide Guarantees [Member] Total Schedule of Insured Financial Obligations with Credit Deterioration, Reductions of Gross Claim Liability, Net Potential Recoveries Schedule of Insured Financial Obligations with Credit Deterioration, Reductions of Gross Claim Liability, Net Potential Recoveries Local Phone Number Local Phone Number Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Total expected future loss and LAE Financial Guarantee Insurance Contracts, Net Loss to be Expensed, Undiscounted Financial Guarantee Insurance Contracts, Net Loss to be Expensed, Undiscounted Other Payment for (Proceeds from) Other Investing Activity Common share repurchases (in shares) Stock Repurchased and Retired During Period, Shares Credit Derivatives Contract Type [Domain] Credit Derivatives Contract Type [Domain] Surrenders and withdrawals Policyholder Account Balance, Surrender and Withdrawal Cash Business Combination, Recognized Asset Acquired, Cash and Cash Equivalent Assets Assets [Abstract] Maturities and paydowns Proceeds from Maturities, Prepayments and Calls of Short-Term Investments Underlying Security Market Price Change Underlying Security Market Price Change, Percent Other Commitments [Axis] Other Commitments [Axis] Fair Value Measurement Fair Value Disclosures [Text Block] Business Combination [Line Items] Business Combination [Line Items] Investment, Name [Axis] Investment, Name [Axis] Additions for securities for which credit losses were not previously recognized Debt Securities, Available-for-Sale, Excluding Accrued Interest, Allowance for Credit Loss, Not Previously Recorded Sound Point Capital Management, LP Sound Point Sound Point Capital Management, LP [Member] Sound Point Capital Management, LP Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Table] Policyholder Account Balance, Guaranteed Minimum Crediting Rate [Table] Entity Registrant Name Entity Registrant Name Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Deferred premium revenue Schedule of Insured Financial Obligations with Credit Deterioration, Statement of Financial Position Unearned Premium Revenue [Abstract] -- None. No documentation exists for this element. -- Gross Premium Receivable, Net of Commissions Payable on Assumed Business Roll Forward Financial Guarantee Insurance Contracts, Premium Receivable Activity [Table Text Block] Tabular disclosure of premium receivable activity with respect to financial guarantee insurance contracts. New York Stock Exchange NEW YORK STOCK EXCHANGE, INC. [Member] Trading Activity [Axis] Trading Activity [Axis] Reconciliation of cash and cash equivalents and restricted cash to the condensed consolidated balance sheets: Reconciliation of Cash and Restricted Cash to Consolidate Balance Sheet [Abstract] Reconciliation of Cash and Restricted Cash to Consolidate Balance Sheet Gain Contingency, Nature [Domain] Gain Contingency, Nature [Domain] Total assets carried at fair value Assets, Fair Value Disclosure Financial Instrument, Other Financial Instrument, Other [Member] Reconciliation of Other Significant Reconciling Items from Segments to Consolidated Segment, Reconciliation of Other Items from Segments to Consolidated [Table Text Block] Number of securities Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions Assets held-in-trust Asset, Held-in-Trust 2026 (July 1 - September 30) Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed During Third Quarter Following Balance Sheet Date Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed During Third Quarter Following Balance Sheet Date Structured finance Structured Finance [Member] Principal Schedule of Insured Financial Obligations with Credit Deterioration, Insured Contractual Payments Outstanding Principal [Abstract] -- None. No documentation exists for this element. -- Related Party [Axis] Related and Nonrelated Parties [Axis] Future accretion Total Schedule of Insured Financial Obligations with Credit Deterioration, Reductions of Gross Claim Liability, Net of Reinsurance Recoverable, Discount (Accretion) Schedule of Insured Financial Obligations with Credit Deterioration, Reductions of Gross Claim Liability, Net of Reinsurance Recoverable, Discount (Accretion) Reconciling items: Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment [Member] Ownership interest Asset Management, Ownership Interest Asset Management, Ownership Interest Unpaid principal balance for FG VIEs’ assets that were 90 days or more past due Fair Value, Option, Loans Held as Assets, 90 Days or More Past Due Restatement Determination Date: Restatement Determination Date [Axis] 2041-2045 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, after Year 15 Through 20 Other Puerto Rico Exposure Non-Defaulting Puerto Rico Exposures [Member] Non-Defaulting Puerto Rico Exposures Net par outstanding, credit derivative Net Par Outstanding Financial Guaranty Contracts Accounted for as Credit Derivatives Outstanding Principal Amount Represents the outstanding principal amounts of the underlying insured obligations that are accounted for as credit derivatives, net of protection purchased. Gain on deconsolidation Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax Weighted-average period of premiums receivable (in years) Financial Guarantee Insurance Contracts, Premium Received over Contract Period, Premium Receivable, Weighted Average Collection Period 2041-2045 Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, after Year 15 Through 20 Due after five years through 10 years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost Number of risks Schedule of Insured Financial Obligations with Credit Deterioration, Number of Risks [Abstract] -- None. No documentation exists for this element. -- Other Proceeds from (Payment for) Other Financing Activity Liabilities assumed: Business Combination, Recognized Liability Assumed, Liability [Abstract] Total amount reclassified from AOCI, net of tax Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Investments with credit impairment, tax Other Comprehensive Income (Loss), Available-for-sale Securities, With Credit Impairment, Tax Other Comprehensive Income (Loss), Available-for-sale Securities, With Credit Impairment, Tax Name Trading Arrangement, Individual Name Underlying Asset Class [Domain] Underlying Asset Class [Domain] Financial guaranty variable interest entities liabilities, fair value Variable Interest Entity, Consolidated, Carrying Amount, Liabilities. Fair Value Disclosure Variable Interest Entity, Consolidated, Carrying Amount, Liabilities. Fair Value Disclosure Bank profit (in bps) Bank Profit [Member] Bank Profit Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Change in unrealized gains/(losses) included in OCI related to financial instruments Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI 2041-2045 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year 15 Through 20 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year 15 Through 20 FG VIEs' assets Financial Guarantee Variable Interest Entities [Member] Financial Guarantee Variable Interest Entities [Member] Cash and cash equivalents of consolidated investment vehicles Cash of Consolidated Investment Vehicles Cash of Consolidated Investment Vehicles Name Awards Close in Time to MNPI Disclosures, Individual Name Implied Yield Measurement Input, Implied Yield [Member] Measurement Input, Implied Yield Schedule of Expected Losses to be Paid [Table] Schedule of Expected Losses to be Paid [Table] Schedule of Expected Losses to be Paid [Table] Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Outstanding commitments to provide guaranties Other Commitment Discount Schedule of Insured Financial Obligations with Credit Deterioration Reductions of Gross Claim Liability, Net Discount [Abstract] -- None. No documentation exists for this element. -- Fixed-maturity investments, non-investment grade, percent Fixed-Maturity Investments, Non-Investment Grade, Not Rated, Percent Fixed-Maturity Investments, Non-Investment Grade, Not Rated, Percent Change in estimate for increased conditional default rate plateau period Loss Estimate Sensitivity Analysis Change in Estimate for Increased Conditional Default Rate Plateau Period Represents the change in expected loss on a pool of insured obligations that would result from an increase in the conditional default rate plateau period. Alternative investment Alternative Investment Estimated Fair Value Debt Securities, Available-for-Sale, Maturity, Fair Value, Rolling Maturity [Abstract] Financial guaranty variable interest entities’ liabilities (includes $152 and $197, at fair value, $178 and $182 with recourse, $16 and $16 without recourse) FG VIEs’ liabilities Financial Guaranty Of Variable Interest Entities, Liability Held Financial Guaranty Of Variable Interest Entities, Liability Held Acquired assets, weighted average useful life Acquired Assets, Weighted Average Useful Life Acquired Assets, Weighted Average Useful Life Liability Class [Axis] Liability Class [Axis] Litigation Case [Axis] Litigation Case [Axis] 2051-2055 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, after Year 25 Through 30 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, after Year 25 Through 30 Segments [Domain] Segments [Domain] Statement of Income Location, Balance [Axis] Statement of Income Location, Balance [Axis] Fixed-maturity securities, available-for-sale: Fixed Maturities [Member] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] Consolidated Entity Excluding Variable Interest Entities (VIE) Consolidated Entity, Excluding Consolidated VIE [Member] Expected LAE to be paid Expected Loss Adjustment Expense To Be Paid Expected Loss Adjustment Expense To Be Paid Insurance Insurance Contracts [Member] Insurance Contracts [Member] Financial Guaranty Variable Interest Entities Financial Guaranty Variable Interest Entities [Member] Financial Guaranty Variable Interest Entities Policyholder account balances for annuity reinsurance contracts Balance, beginning of year Balance, end of period Policyholder account balances for annuity reinsurance contracts Policyholder Account Balance Other, net of tax provision (benefit) Other Comprehensive Income (Loss), Other, Net of Tax, Portion Attributable To Parent Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent and Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent Purchases Payments to Acquire Debt Securities, Available-for-Sale 2041-2045 Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed More than 14 and within 19 Years from Balance Sheet Date Financial Guarantee Insurance Contracts Future Expected Net Loss to be Expensed More than 14 and within 19 Years from Balance Sheet Date Financial guaranty variable interest entities’ assets (includes $167 and $172, at fair value) Financial Guaranty Of Variable Interest Entities, Assets Held Financial Guaranty Of Variable Interest Entities, Assets Held Obligations of state and political subdivisions US States and Political Subdivisions Debt Securities [Member] Gross Insured Financial Obligations Outstanding Principal Amount, Gross Represents the outstanding principal amounts of the underlying insured obligations for financial guaranty contracts, gross of ceded contracts. Total liabilities Business Combination, Recognized Liability Assumed, Liability All Executive Categories All Executive Categories [Member] Amortization of deferred acquisition costs Segment amortization of deferred acquisition costs Deferred Policy Acquisition Costs, Amortization Expense Common shares ($0.01 par value, 500,000,000 shares authorized; 44,591,054 and 45,184,791 shares issued and outstanding) Common Stock, Value, Issued Short-term investments, at fair value Short-Term Investments Net earned premiums Net earned premiums Premiums Earned, Net Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Net Realized Investment Gains (Losses) Realized Gain (Loss) on Investments [Table Text Block] Collateralized Loan Obligation Equity Tranches Collateralized Loan Obligation Equity Tranches [Member] Collateralized Loan Obligation Equity Tranches Commitments and contingencies (Notes 4, 5, 9 and 13) Commitments and Contingencies Foreign exchange gain (loss) on remeasurement Financial Guarantee Insurance Contracts, Premiums Receivable Adjustment Foreign Exchange Translation Represents gains or losses due to foreign exchange rate changes that relate to installment premium receivables on financial guaranty insurance contracts denominated in currencies other than U.S. dollar. Business Combination [Axis] Business Combination [Axis] Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Non-redeemable Noncontrolling Interest Noncontrolling Interest [Member] 2029 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Year Four Realized gains (losses) and other settlements Credit Derivative, Realized Gain (Loss) and Other Settlements Represents the premiums received and receivable, ceding commissions, and the losses paid and payable. This element refers to the gain (loss) included in earnings. Net Investment Income Investment Income [Table Text Block] Short-term investments Short-Term Investments [Member] Total pre-tax realized and unrealized gains (losses) recorded in: Total Pretax Realized And Unrealized Gains (Losses) Recorded As Liabilities [Abstract] Total Pretax Realized And Unrealized Gains (Losses) Recorded As Liabilities [Abstract] Reconciliation of Net Expected Loss to be Paid and Net Expected Loss to be Expensed Financial Guaranty Insurance Contracts Reconciliation of Net Expected Loss to be Paid and Net Expected Loss to be Expensed [Table Text Block] Tabular disclosure of the reconciliation of expected loss to be paid and net expected loss to be expensed. Subtotal 2026 Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year One Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable, Year One Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Gains (losses) on financial guaranty variable interest entities Variable Interest Entity, Change in Fair Value The amount of the variable interest entity's revenues consolidated into the statement of income, including interest income, net realized and unrealized gains (losses) on assets, and other income, net of the amount of the variable interest entity's expenses consolidated into the statement of income, including interest expense, net realized and unrealized gains (losses) on liabilities with and without recourse, and other expenses. Diluted EPS: Earnings Per Share, Diluted [Abstract] 2031-2035 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, after Year 5 Through 10 AA Internal Investment Grade, AA [Member] The entity's internal risk assessment category, AA, representing the third lowest risk level. 1 Net par outstanding, financial guaranty insurance Total Schedule of Insured Financial Obligations with Credit Deterioration Insured Contractual Payments Outstanding Principal Net This element represents the amount of insured contractual payments outstanding attributable to the principal of the underlying insured obligations for financial guaranty insurance contracts presented in the context of each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guaranty insurance contracts, before adjusting for the effect of consolidating VIEs. Assured Guaranty US Holdings Inc. 3.150% Senior Notes due 2031 (and the related guarantee of Registrant) Assured Guaranty US Holdings Inc. 3.150% Senior Notes due 2031 [Member] Assured Guaranty US Holdings Inc. 3.150% Senior Notes due 2031 Scenario [Axis] Scenario [Axis] Surveillance Category [Domain] Surveillance Category [Domain] 2028 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Year Three Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Year Three Financial Guaranty Financial Guaranty Segment [Member] Pooled corporate obligations Pooled Corporate Obligation [Member] Pooled Corporate Obligation Total (in years) Schedule of Insured Financial Obligations with Credit Deterioration, Remaining Weighted Average Contract Period, Net This element represents the remaining weighted average contract period of financial guaranty insurance contracts for each surveillance grouping or category used by management to monitor and track potential deterioration in the credit worthiness of the insured party's ability to meet its financial obligations related to the contracts underlying financial guaranty insurance contracts, before adjusting for the effect of consolidating VIEs. 2028 Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, Year Three Derivative Contract [Domain] Derivative Contract [Domain] Sales of and return of capital from other invested assets Proceeds from Sale of Other Assets, Investing Activities Gross realized losses on sales of available-for-sale securities Debt Securities, Available-for-Sale, Realized Loss All Individuals All Individuals [Member] Schedule of Insured Financial Obligations with Credit Deterioration [Table] Financial Guarantee Insurance Contracts, Claim Liability [Table] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Name Forgone Recovery, Individual Name Roll Forward of Credit Losses in the Investment Portfolio Debt Securities, Available-for-Sale, Allowance for Credit Loss [Roll Forward] Net unrealized gains (losses) Unrealized Gain (Loss) on Derivatives Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] 2026 (July 1 - September 30) Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Third Quarter Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Third Quarter Recourse Recourse [Member] Sales of fixed-maturity securities, trading Proceeds from (Payments for) Trading Securities, Short-Term Unencumbered Asset Unencumbered Asset Unencumbered Assets which are not held in trust for the benefit of cedants. Net expected loss to be expensed (present value) Net expected loss to be expensed (present value) Financial Guarantee Insurance Contracts, Net Loss to be Expensed, Present Value Financial Guarantee Insurance Contracts, Net Loss to be Expensed, Present Value Loss and LAE Reported on the Consolidated Statements of Operations Financial Guaranty Insurance Contracts Loss and Loss Adjustment Expense Amounts Included in Earnings [Table Text Block] Tabular disclosure of the loss and loss adjustment expense for financial guaranty insurance contracts including in earnings, by sector. 2027 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Year Two Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Net, Year Two 2026 (October 1 - December 31) Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, Fourth Quarter Financial guaranty variable interest entities' assets, fair value Financial Guaranty Of Variable Interest Entities, Fair Value Disclosure Financial Guaranty Of Variable Interest Entities, Fair Value Disclosure Short-term investments, at fair value Other Short-Term Investments Schedule of Derivative Instruments Schedule of Derivative Instruments [Table Text Block] Liability for Future Policy Benefit Activity [Table] Liability for Future Policy Benefit Activity [Table] Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Specialty net earned premiums Premiums Earned, Net, Specialty Insurance and Reinsurance Premiums Earned, Net, Specialty Insurance and Reinsurance Geographical [Axis] Geographical [Axis] Accumulated other comprehensive income (loss), tax provision AOCI Tax, Attributable to Parent BBB Internal Investment Grade, BBB [Member] Internal Investment Grade, BBB [Member] Assets of consolidated investment vehicles, fair value disclosure Assets of Consolidated Investment Vehicles, Fair Value Disclosure Assets of Consolidated Investment Vehicles, Fair Value Disclosure Gross Insured Financial Obligations Insured Contractual Payments Outstanding, Gross Represents the amount of insured contractual payments (principal and interest) outstanding on the underlying insured obligations for direct financial guaranty contracts. Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Pro forma revenue Business Combination, Pro Forma Information, Pro Forma Revenue Foreign exchange gains (losses) on remeasurement Gain (Loss), Foreign Currency Transaction, before Tax Forecast Forecast [Member] Less: Distributed and undistributed income (loss) available to nonvested shareholders Participating Securities, Distributed and Undistributed Earnings (Loss), Basic Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Title of 12(b) Security Title of 12(b) Security Due within one year Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost Total Financial Guarantee Insurance Contracts, Premium Receivable, Premium Expected to be Collected BIG Internal Noninvestment Grade [Member] Earnings per share: Earnings Per Share [Abstract] Statutory Accounting Practice, Jurisdiction [Domain] Statutory Accounting Practice, Jurisdiction [Domain] Total pre-tax realized and unrealized gains (losses) recorded in: Total Pretax Realized And Unrealized Gains (Losses) Recorded As Net Derivative Asset (Liability) [Abstract] Total Pretax Realized And Unrealized Gains (Losses) Recorded As Net Derivative Asset (Liability) [Abstract] Change in unrealized gains/(losses) included in earnings related to financial instruments Fair Value, Net Derivative Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss) Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Scheduled net earned premiums Financial Guarantee Insurance Contracts Scheduled, Net Earned Premiums Represents the amount of premium revenue on financial guaranty insurance contracts recognized during the period, excluding acceleration of premium earnings and accretion of discount on net premium receivable. Funds withheld - embedded derivative Embedded Derivative Financial Instruments [Member] Annuity Reinsurance Annuity Reinsurance [Member] Annuity Reinsurance U.K. National Health Service Trusts U.K. National Health Service Trusts [Member] U.K. National Health Service Trusts Dilutive securities: Weighted Average Number of Shares Outstanding, Diluted, Adjustment [Abstract] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Award Timing Disclosures [Line Items] Plus: Re-allocation of undistributed income (loss) available to nonvested shareholders of AGL and subsidiaries Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted Fair value gains (losses) on committed capital securities Fair Value, Gain (Loss) On Committed Capital Securities Fair Value, Gain (Loss) On Committed Capital Securities AG Financial Products Inc. Assured Guaranty Financial Products Inc [Member] Assured Guaranty Financial Products Inc [Member] Measurement Frequency [Domain] Measurement Frequency [Domain] FG VIEs’ liabilities without recourse Fair Value, Option, Loans Held as Liabilities, Aggregate Difference, Without Recourse Fair Value, Option, Loans Held as Liabilities, Aggregate Difference, Without Recourse Loss and LAE reserve - FG insurance contracts, net of reinsurance Liability for Unpaid Claims and Claims Adjustment Expense, Net Loss severity Measurement Input, Loss Severity [Member] Shareholders' Equity Equity [Text Block] Maximum amount Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Maximum Amount Gross Schedule of Insured Financial Obligations with Credit Deterioration, Reductions of Gross Claim Liability, Net Discount Net income (loss) attributable to Assured Guaranty Ltd. Net Income (Loss) Attributable to AGL Net income (loss) attributable to AGL Net Income (Loss) Attributable to Parent CLOs Collateralized Loan Obligations [Member] Credit Deterioration Surveillance Category [Axis] Credit Deterioration Surveillance Category [Axis] Pending Litigation Pending Litigation [Member] Total Credit Default Swap [Member] Investments, authorized amount to invest Investments, Authorized Amount To Invest Investments, Authorized Amount To Invest Lehman Brothers International (Europe) Lehman Brothers International (Europe) [Member] Lehman Brothers International (Europe) [Member] Investments with credit impairment, net of tax provision (benefit) of $(11) and $5 Other Comprehensive Income (Loss), Available-For-Sale Securities, With Credit Impairment, Net Of Tax Other Comprehensive Income (Loss), Available-For-Sale Securities, With Credit Impairment, Net Of Tax Market multiple-price to book Measurement Input, Exit Multiple, Price To Book [Member] Measurement Input, Exit Multiple, Price To Book Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Repurchases of common shares Repurchases of common stock Payments for Repurchase of Common Stock Adoption Date Trading Arrangement Adoption Date Contract asset related to service agreement Contract with Customer, Asset, after Allowance for Credit Loss Write-offs charged against the allowance Debt Securities, Available-for-Sale, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff Term (years) Measurement Input, Expected Term [Member] Additional amount authorized Share Repurchase Program, Additional Amount Authorized Share Repurchase Program, Additional Amount Authorized Quoted price of CDS contract (as a percent) Credit Derivative Quoted Price Represents the quoted price of credit derivative contracts. Segment adjusted operating income (loss) Operating Income (Loss) Total number of entities consolidated Variable Interest Entity, Number of Entities Consolidated Variable Interest Entity, Number of Entities Consolidated Retained earnings Retained Earnings (Accumulated Deficit) Other structured finance Other Structured Finance [Member] Represents structured finance obligations not separately disclosed. Policyholder Account Balance, at Guaranteed Minimum Crediting Rate Policyholder Account Balance, at Guaranteed Minimum Crediting Rate [Member] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Schedule of BIG Net Par Outstanding and Number of Risks Schedule Of Insured Financial Obligations, Below Investment Grade [Table Text Block] Schedule Of Insured Financial Obligations, Below Investment Grade [Table Text Block] Deconsolidations Fair Value Measurement with Unobservable Inputs, Reconciliation, Recurring Basis Asset, Deconsolidations Fair Value Measurement with Unobservable Inputs, Reconciliation, Recurring Basis Asset, Deconsolidations Gross Schedule of Insured Financial Obligations with Credit Deterioration, Insured Contractual Payments Outstanding, Principal Subtotal 2026 Financial Guarantee Insurance Contracts, Future Expected Premium Revenue to be Recognized, Fiscal Year Financial Guarantee Insurance Contracts, Future Expected Premium Revenue to be Recognized, Fiscal Year Number of securities Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions Class of Stock [Axis] Class of Stock [Axis] Cash Flow  Hedge Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Net (paid) recovered losses Guarantor Obligations, Liability For Unpaid Claims And Claims Adjustment Expense, Claims Paid After Recoveries for Representations and Warranties Guarantor Obligations, Liability For Unpaid Claims And Claims Adjustment Expense, Claims Paid After Recoveries for Representations and Warranties Credit Derivatives Credit Derivatives [Line Items] Schedule of Insured Financial Obligations [Line Items] Schedule of Insured Financial Obligations [Line Items] [Line Items] for Schedule of Insured Financial Obligations [Table] Statement [Table] Statement [Table] Cash flows from financing activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Funds withheld, measurement input Funds Withheld, Measurement Input Funds Withheld, Measurement Input Number of policies that contain provisions for consolidation Variable Interest Entity, Number of Policies that Contain Provisions for Consolidation Variable Interest Entity, Number of Policies that Contain Provisions for Consolidation Projected loss assumptions, CDR, plateau rate, projection period Guarantor Obligations, Projected Loss Assumptions, Conditional Default Rate, Plateau Rate, Projection Period Represents the period over which the application of the constant conditional default rate would produce approximately the amount of defaults calculated for each delinquency category of insured financial obligations. Fair Value Assets Measured on Recurring Basis Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Salvage and subrogation recoverable Salvage and Subrogation Recoveries, Value All Adjustments to Compensation All Adjustments to Compensation [Member] Amendment Flag Amendment Flag Other Comprehensive Income Location [Axis] Other Comprehensive Income Location [Axis] Loss and loss adjustment expense reserve Liability for Claims and Claims Adjustment Expense Termination Date Trading Arrangement Termination Date Assured Life Re Acquisition, January 21, 2026 Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Net foreign currency gains (losses) Realized Gain (Loss), Foreign Currency Transaction, before Tax Subtotal 2026 Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, Year One Accretion of discount, net of commissions on assumed business Financial Guarantee Insurance Contracts, Premiums Receivable, Adjustment, Accretion of Discount on Premium Receivable Acquiree's revenue since acquisition date, actual Business Combination, Acquiree's Revenue since Acquisition Date, Actual Basic shares (in shares) Weighted Average Number of Shares Outstanding, Basic Net Investment Income Investment Income, Net [Abstract] Schedule of Computation of Basic and Diluted Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] 2030 Financial Guarantee Insurance Contract, Premium Revenue to be Recognized, Year Five Segment Reporting [Abstract] Segment Reporting [Abstract] Operating Segments Excluding Intersegment Elimination Operating Segments Excluding Intersegment Elimination [Member] Operating Segments Excluding Intersegment Elimination Distributions to noncontrolling interest from consolidated investment vehicles Distributions To Noncontrolling Interests From Investment Vehicles Distributions To Noncontrolling Interests From Investment Vehicles Credit derivatives Financial Guarantee Accounted for as Credit Derivatives [Member] Financial Guarantee Accounted for as Credit Derivatives [Member] Scenario [Domain] Scenario [Domain] Tax (provision) benefit Reclassification from AOCI, Current Period, Tax Expected future benefit payments, discounted Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance Range of Guaranteed Minimum Crediting Rate Policyholder Account Balance, Guaranteed Minimum Credit Rating Reconciling Items [Axis] Reconciling Items [Axis] Reconciling Items Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Net Reserve (Recoverable) Reserve for Losses and Loss Adjustment Expenses, Net of Reinsurance and Salvage and Subrogation Recoveries Represents the reserve for losses and loss adjustment expenses, net of reinsurance recoverable on unpaid losses and net of salvage and subrogation recoverable. Consolidated Entities [Axis] Consolidated Entities [Axis] Common stock par value (in dollars per share) Common Stock, Par or Stated Value Per Share Gross Schedule of Insured Financial Obligations with Credit Deterioration, Statement of Financial Position, Unearned Premium Revenue Change in discount rates on future policy benefits for annuity reinsurance contracts, net of tax provision (benefit) of $4 and $— OCI, Liability for Future Policy Benefit, Gain (Loss), after Reclassification Adjustment and Tax Changes in discount rates Guarantor Obligations, Net Expected Loss Development After Recoveries for Representations and Warranties, Changes In Discount Rates Guarantor Obligations, Net Expected Loss Development After Recoveries for Representations and Warranties, Changes In Discount Rates Deferred loan balances to be recovered, least stressful environment, percent Guarantor Obligations, Projected Loss Assumption, Deferred Loan Balances to be Recovered, Least Stressful Environment, Percent Guarantor Obligations, Projected Loss Assumption, Deferred Loan Balances to be Recovered, Least Stressful Environment, Percent Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Fair Value Hierarchy of Financial Instruments Carried at Fair Value Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] Fixed-maturity securities, available-for-sale: Payments for (Proceeds from) Investments [Abstract] Insider Trading Arrangements [Line Items] 2051-2055 Financial Guarantee Insurance Contract, Premium Receivable, to be Collected, after Year 25 Through 30 Assets of CIVs Exit multiple-price to book Equity Securities [Member] Allowance for credit loss Allowance for Credit Losses Balance, beginning of period Balance, end of period Debt Securities, Available-for-Sale, Allowance for Credit Loss, Excluding Accrued Interest LBIE vs. AG Financial Products Lehman Brothers International Europe Vs AG Financial Products Inc [Member] Represents the information pertaining to the case filed by Lehman Brothers International (Europe) against AG Financial Products Inc., an affiliate of AGC. Total liabilities Liabilities Liabilities Settlements Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Settlements Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Termination payments which AG Financial Products owes to LBIE as per calculation of LBIE Gain Contingency, Allegations, Payment For Termination of Credit Derivative Transactions Owed by Defendant to Plaintiff As Per Calculation of Plaintiff Represents the amount of payment on the termination of credit derivatives transactions which the defendant owes to plaintiff as per the calculation of plaintiff. Asset-backed securities Asset-Backed Securities [Member] Consolidation Items [Axis] Consolidation Items [Axis] Policyholder Account Balance Policyholder Account Balance [Table Text Block] Counterparty Name [Axis] Counterparty Name [Axis] Net income Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Non-NEOs Non-NEOs [Member] Corporate securities Corporate Debt Securities [Member] Insured Financial Obligations, Loss Mitigation Securities Insured Financial Obligations, Loss Mitigation Securities [Member] Insured Financial Obligations, Loss Mitigation Securities