Business and Basis of Presentation	9 Months Ended
Sep. 30, 2012
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Basis of Presentation	Business and Basis of Presentation Business Assured Guaranty Ltd. (“AGL” and, together with its subsidiaries, “Assured Guaranty” or the “Company”) is a Bermuda-based holding company that provides, through its operating subsidiaries, credit protection products to the United States (“U.S.”) and international public finance (including infrastructure) and structured finance markets. The Company has applied its credit underwriting judgment, risk management skills and capital markets experience to offer insurance that protects holders of debt instruments and other monetary obligations from defaults in scheduled payments, including scheduled interest and principal payments. The Company markets its credit protection products directly to issuers and underwriters of public finance and structured finance securities as well as to investors in such obligations. The Company guarantees obligations issued in many countries, although its principal focus is on the U.S., Europe and Australia. Financial guaranty insurance policies provide an unconditional and irrevocable guaranty that protects the holder of a financial obligation against non-payment of principal and interest ("Debt Service") when due. Upon an obligor’s default on scheduled principal or interest payments due on the obligation, the Company is required under the financial guaranty policy to pay the principal or interest shortfall. The Company has issued financial guaranty insurance policies on public finance obligations and structured finance obligations. Public finance obligations insured by the Company consist primarily of general obligation bonds supported by the taxing powers of U.S. state or municipal governmental authorities, as well as tax-supported bonds, revenue bonds and other obligations supported by covenants from state or municipal governmental authorities or other municipal obligors to impose and collect fees and charges for public services or specific infrastructure projects. The Company also includes within public finance obligations those obligations backed by the cash flow from leases or other revenues from projects serving substantial public purposes, including utilities, toll roads, health care facilities and government office buildings. Structured finance obligations insured by the Company are generally issued by special purpose entities and backed by pools of assets such as residential or commercial mortgage loans, consumer or trade receivables, securities or other assets having an ascertainable cash flow or market value. The Company also includes within structured finance obligations other specialized financial obligations. In the past, the Company had sold credit protection by issuing policies that guaranteed payment obligations under credit derivatives. Financial guaranty contracts accounted for as credit derivatives are generally structured such that the circumstances giving rise to the Company’s obligation to make loss payments are similar to those for financial guaranty insurance contracts and only occurs upon one or more defined credit events such as failure to pay or bankruptcy, in each case, as defined within the transaction documents, with respect to one or more third party referenced securities or loans. Financial guaranty contracts accounted for as credit derivatives are primarily comprised of credit default swaps (“CDS”). The Company’s credit derivative transactions are governed by International Swaps and Derivative Association, Inc. (“ISDA”) documentation. The Company has not entered into any new CDS in order to sell credit protection since the beginning of 2009, when regulatory guidelines were issued that limited the terms under which such protection could be sold. The capital and margin requirements applicable under the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”) also contributed to the decision of the Company not to enter into such new CDS in the foreseeable future. The Company actively pursues opportunities to terminate existing CDS and, in certain cases, has converted existing CDS exposure into a financial guaranty insurance contract. These actions have the effect of reducing future fair value volatility in income and/or reducing rating agency capital charges. The Company has historically entered into ceded reinsurance contracts in order to obtain greater business diversification and reduce the net potential loss from large risks. In January 2012, two of AGL's operating subsidiaries, Assured Guaranty Municipal Corp. (“AGM”) and Assured Guaranty Corp. (“AGC”), entered into a $435 million excess of loss reinsurance facility with third-party reinsurers, which reduced rating agency capital charges. The Company also has been reassuming previously ceded business from reinsurers. In the three-month period ended March 31, 2012 (“First Quarter 2012”), the Company reassumed a total of $19.1 billion in par from two reinsurers and in the three-month period ended September 30, 2012, the Company reassumed $9 million in par from one reinsurer. See Note 11, Reinsurance and Other Monoline Exposures. When a rating agency assigns a public rating to a financial obligation guaranteed by one of AGL’s insurance company subsidiaries, it generally awards that obligation the same rating it has assigned to the financial strength of the AGL subsidiary that provides the guaranty. Investors in products insured by AGL’s insurance company subsidiaries frequently rely on ratings published by nationally recognized statistical rating organizations (“NRSROs”) because such ratings influence the trading value of securities and form the basis for many institutions’ investment guidelines as well as individuals’ bond purchase decisions. Therefore, the Company manages its business with the goal of achieving high financial strength ratings. However, the models used by NRSROs differ, presenting conflicting goals that may make it inefficient or impractical to reach the highest rating level. The models are not fully transparent, contain subjective data (such as assumptions about future market demand for the Company’s products) and change frequently. Ratings reflect only the views of the respective NRSROs and are subject to continuous review and revision or withdrawal at any time. Unless otherwise noted, ratings disclosed herein on Assured Guaranty’s insured portfolio reflect Assured Guaranty’s internal ratings. Assured Guaranty’s ratings scale is similar to that used by the NRSROs; however, the ratings in these financial statements may not be the same as those assigned by any such rating agency. For example, the super senior category, which is not generally used by rating agencies, is used by Assured Guaranty in instances where Assured Guaranty’s AAA-rated exposure on its internal rating scale (which does not take into account Assured Guaranty’s financial guaranty) has additional credit enhancement due to either (1) the existence of another security rated AAA that is subordinated to Assured Guaranty’s exposure or (2) Assured Guaranty’s exposure benefiting from a different form of credit enhancement that would pay any claims first in the event that any of the exposures incurs a loss, and such credit enhancement, in management’s opinion, causes Assured Guaranty’s attachment point to be materially above the AAA attachment point. Basis of Presentation The unaudited interim consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and, in the opinion of management, reflect all adjustments that are of a normal recurring nature, necessary for a fair statement of the financial condition, results of operations and cash flows of the Company and its consolidated financial guaranty variable interest entities (“FG VIEs”) for the periods presented. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. These unaudited interim consolidated financial statements are as of September 30, 2012 and cover the three-month period ended September 30, 2012 ("Third Quarter 2012"), the three-month period ended September 30, 2011 ("Third Quarter 2011"), the nine-month period ended September 30, 2012 ("Nine Months 2012") and the nine-month period ended September 30, 2011 ("Nine Months 2011"). The year-end balance sheet data was derived from audited financial statements, but does not include all disclosures required by GAAP. The unaudited interim consolidated financial statements include the accounts of AGL and its direct and indirect subsidiaries (collectively, the “Subsidiaries”) and its consolidated FG VIEs. Intercompany accounts and transactions between and among all consolidated entities have been eliminated. Certain prior year balances have been reclassified to conform to the current year’s presentation. These unaudited interim consolidated financial statements should be read in conjunction with the consolidated financial statements included in AGL’s Annual Report on Form 10-K for the year ended December 31, 2011, filed with the U.S. Securities and Exchange Commission (the “SEC”). AGL’s principal insurance company subsidiaries are AGC, domiciled in Maryland; AGM, domiciled in New York; and Assured Guaranty Re Ltd. (“AG Re”), domiciled in Bermuda. In addition, the Company has another U.S. and another Bermuda insurance company subsidiary that participate in a pooling agreement with AGM, two insurance subsidiaries organized in the United Kingdom, and a mortgage insurance company domiciled in New York. On May 31, 2012, the Company also completed the purchase of Municipal and Infrastructure Assurance Corporation ("MIAC"), which is domiciled in New York. See Note 2, Business Changes, Risks, Uncertainties and Accounting Developments. The Company’s organizational structure includes various holdings companies, two of which—Assured Guaranty US Holdings Inc. (“AGUS”) and Assured Guaranty Municipal Holdings Inc. (“AGMH”)—have public debt outstanding. See Note 13, Long Term Debt and Credit Facilities.

Business and Basis of Presentation

Business

Assured Guaranty Ltd. (“AGL” and, together with its subsidiaries, “Assured Guaranty” or the “Company”) is a Bermuda-based holding company that provides, through its operating subsidiaries, credit protection products to the United States (“U.S.”) and international public finance (including infrastructure) and structured finance markets. The Company has applied its credit underwriting judgment, risk management skills and capital markets experience to offer insurance that protects holders of debt instruments and other monetary obligations from defaults in scheduled payments, including scheduled interest and principal payments. The Company markets its credit protection products directly to issuers and underwriters of public finance and structured finance securities as well as to investors in such obligations. The Company guarantees obligations issued in many countries, although its principal focus is on the U.S., Europe and Australia.

Financial guaranty insurance policies provide an unconditional and irrevocable guaranty that protects the holder of a financial obligation against non-payment of principal and interest ("Debt Service") when due. Upon an obligor’s default on scheduled principal or interest payments due on the obligation, the Company is required under the financial guaranty policy to pay the principal or interest shortfall. The Company has issued financial guaranty insurance policies on public finance obligations and structured finance obligations. Public finance obligations insured by the Company consist primarily of general obligation bonds supported by the taxing powers of U.S. state or municipal governmental authorities, as well as tax-supported bonds, revenue bonds and other obligations supported by covenants from state or municipal governmental authorities or other municipal obligors to impose and collect fees and charges for public services or specific infrastructure projects. The Company also includes within public finance obligations those obligations backed by the cash flow from leases or other revenues from projects serving substantial public purposes, including utilities, toll roads, health care facilities and government office buildings. Structured finance obligations insured by the Company are generally issued by special purpose entities and backed by pools of assets such as residential or commercial mortgage loans, consumer or trade receivables, securities or other assets having an ascertainable cash flow or market value. The Company also includes within structured finance obligations other specialized financial obligations.

In the past, the Company had sold credit protection by issuing policies that guaranteed payment obligations under credit derivatives. Financial guaranty contracts accounted for as credit derivatives are generally structured such that the circumstances giving rise to the Company’s obligation to make loss payments are similar to those for financial guaranty insurance contracts and only occurs upon one or more defined credit events such as failure to pay or bankruptcy, in each case, as defined within the transaction documents, with respect to one or more third party referenced securities or loans. Financial guaranty contracts accounted for as credit derivatives are primarily comprised of credit default swaps (“CDS”). The Company’s credit derivative transactions are governed by International Swaps and Derivative Association, Inc. (“ISDA”) documentation.

The Company has not entered into any new CDS in order to sell credit protection since the beginning of 2009, when regulatory guidelines were issued that limited the terms under which such protection could be sold. The capital and margin requirements applicable under the Dodd-Frank Wall Street Reform and Consumer Protection Act (the “Dodd-Frank Act”) also contributed to the decision of the Company not to enter into such new CDS in the foreseeable future. The Company actively pursues opportunities to terminate existing CDS and, in certain cases, has converted existing CDS exposure into a financial guaranty insurance contract. These actions have the effect of reducing future fair value volatility in income and/or reducing rating agency capital charges.

The Company has historically entered into ceded reinsurance contracts in order to obtain greater business diversification and reduce the net potential loss from large risks. In January 2012, two of AGL's operating subsidiaries, Assured Guaranty Municipal Corp. (“AGM”) and Assured Guaranty Corp. (“AGC”), entered into a $435 million excess of loss reinsurance facility with third-party reinsurers, which reduced rating agency capital charges. The Company also has been reassuming previously ceded business from reinsurers. In the three-month period ended March 31, 2012 (“First Quarter 2012”), the Company reassumed a total of $19.1 billion in par from two reinsurers and in the three-month period ended September 30, 2012, the Company reassumed $9 million in par from one reinsurer. See Note 11, Reinsurance and Other Monoline Exposures.

When a rating agency assigns a public rating to a financial obligation guaranteed by one of AGL’s insurance company subsidiaries, it generally awards that obligation the same rating it has assigned to the financial strength of the AGL subsidiary that provides the guaranty. Investors in products insured by AGL’s insurance company subsidiaries frequently rely on ratings published by nationally recognized statistical rating organizations (“NRSROs”) because such ratings influence the trading value of securities and form the basis for many institutions’ investment guidelines as well as individuals’ bond purchase decisions. Therefore, the Company manages its business with the goal of achieving high financial strength ratings. However, the models used by NRSROs differ, presenting conflicting goals that may make it inefficient or impractical to reach the highest rating level. The models are not fully transparent, contain subjective data (such as assumptions about future market demand for the Company’s products) and change frequently. Ratings reflect only the views of the respective NRSROs and are subject to continuous review and revision or withdrawal at any time.

Unless otherwise noted, ratings disclosed herein on Assured Guaranty’s insured portfolio reflect Assured Guaranty’s internal ratings. Assured Guaranty’s ratings scale is similar to that used by the NRSROs; however, the ratings in these financial statements may not be the same as those assigned by any such rating agency. For example, the super senior category, which is not generally used by rating agencies, is used by Assured Guaranty in instances where Assured Guaranty’s AAA-rated exposure on its internal rating scale (which does not take into account Assured Guaranty’s financial guaranty) has additional credit enhancement due to either (1) the existence of another security rated AAA that is subordinated to Assured Guaranty’s exposure or (2) Assured Guaranty’s exposure benefiting from a different form of credit enhancement that would pay any claims first in the event that any of the exposures incurs a loss, and such credit enhancement, in management’s opinion, causes Assured Guaranty’s attachment point to be materially above the AAA attachment point.

Basis of Presentation

The unaudited interim consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and, in the opinion of management, reflect all adjustments that are of a normal recurring nature, necessary for a fair statement of the financial condition, results of operations and cash flows of the Company and its consolidated financial guaranty variable interest entities (“FG VIEs”) for the periods presented. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. These unaudited interim consolidated financial statements are as of September 30, 2012 and cover the three-month period ended September 30, 2012 ("Third Quarter 2012"), the three-month period ended September 30, 2011 ("Third Quarter 2011"), the nine-month period ended September 30, 2012 ("Nine Months 2012") and the nine-month period ended September 30, 2011 ("Nine Months 2011"). The year-end balance sheet data was derived from audited financial statements, but does not include all disclosures required by GAAP.

The unaudited interim consolidated financial statements include the accounts of AGL and its direct and indirect subsidiaries (collectively, the “Subsidiaries”) and its consolidated FG VIEs. Intercompany accounts and transactions between and among all consolidated entities have been eliminated. Certain prior year balances have been reclassified to conform to the current year’s presentation.

These unaudited interim consolidated financial statements should be read in conjunction with the consolidated financial statements included in AGL’s Annual Report on Form 10-K for the year ended December 31, 2011, filed with the U.S. Securities and Exchange Commission (the “SEC”).

AGL’s principal insurance company subsidiaries are AGC, domiciled in Maryland; AGM, domiciled in New York; and Assured Guaranty Re Ltd. (“AG Re”), domiciled in Bermuda. In addition, the Company has another U.S. and another Bermuda insurance company subsidiary that participate in a pooling agreement with AGM, two insurance subsidiaries organized in the United Kingdom, and a mortgage insurance company domiciled in New York. On May 31, 2012, the Company also completed the purchase of Municipal and Infrastructure Assurance Corporation ("MIAC"), which is domiciled in New York. See Note 2, Business Changes, Risks, Uncertainties and Accounting Developments. The Company’s organizational structure includes various holdings companies, two of which—Assured Guaranty US Holdings Inc. (“AGUS”) and Assured Guaranty Municipal Holdings Inc. (“AGMH”)—have public debt outstanding. See Note 13, Long Term Debt and Credit Facilities.