Represents the number of securities which had unrealized losses greater than 10% of book value for 12 months or more.

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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.

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Represents the continuous period of decline in the market value of a security by any percentage below the amortized cost considered for the assessment of the impairment of investments.

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Investments, Authorized Amount To Invest

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Represents the minimum percentage of decline in the market value of securities below the amortized cost considered for the assessment of the impairment of investments.

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No definition available.

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Number of Outside Managers Managing Investment Portfolio

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- Definition

Interest, dividends, rents, ancillary and other revenues earned but not yet received by the entity on its investments.

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The total amount of cash and securities held by third party trustees pursuant to terms of debt instruments or other agreements as of the date of each statement of financial position presented, which can be used by the trustee only to pay the noncurrent portion of specified obligations.

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Amount of expense for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), for which no credit loss was previously recorded.

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

The minimum amount the entity agreed to spend under the long-term purchase commitment.

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No definition available.

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Dividends received on equity and other investments during the current period.

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Minimum amount to be expended to satisfy the terms of arrangements in which the entity has agreed to expend funds to procure goods or services, excluding long-term purchase commitments or unconditional purchase obligations.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Investments and Cash - Narrative (Details)	12 Months Ended
Investments and Cash - Narrative (Details)	Dec. 31, 2021 USD ($) Security manager	Dec. 31, 2020 USD ($) Security	Dec. 31, 2019 USD ($)
Schedule of Cost-method Investments [Line Items]
Percentage of decline in market value of security below amortized cost, considered for assessing impairment of investments	20.00%
Continuous period of decline in market value of security, considered for assessing impairment of investments	12 months
Number of investment portfolio managers \| manager	3
Accrued investment income	$ 69,000,000	$ 75,000,000
Number of securities with unrealized losses greater than 10% of book value for 12 months or more \| Security	23	11
Total unrealized losses for securities having losses greater than 10% of book value for 12 months or more	$ 6,000,000	$ 8,000,000
Assets held-in-trust	243,000,000	262,000,000
Additions for securities for which credit impairments were not previously recognized	4,000,000	1,000,000
PCI Securities
Schedule of Cost-method Investments [Line Items]
Additions for securities for which credit impairments were not previously recognized	6,000,000	16,000,000
Assured Guaranty Subsidiaries
Schedule of Cost-method Investments [Line Items]
Assets held-in-trust	1,231,000,000	1,511,000,000
Future Equity Investments
Schedule of Cost-method Investments [Line Items]
Purchase commitment, remaining minimum amount committed	95,000,000
AssuredIM Funds \| Equity in Earnings of Investees \| Assured Guaranty Asset Strategies LLC
Schedule of Cost-method Investments [Line Items]
Fair value of investment	543,000,000	345,000,000
AssuredIM Funds \| Equity in Earnings of Investees \| Assured Guaranty Subsidiaries
Schedule of Cost-method Investments [Line Items]
Long-term purchase commitment, amount	702,000,000
AssuredIM Funds \| Future Equity Investments \| Assured Guaranty Subsidiaries
Schedule of Cost-method Investments [Line Items]
Authorized amount to invest	750,000,000
AssuredIM Funds \| Invested Capital \| Assured Guaranty Subsidiaries
Schedule of Cost-method Investments [Line Items]
Long-term purchase commitment, amount	458,000,000
AssuredIM Funds \| Unfunded Commitment \| Assured Guaranty Subsidiaries
Schedule of Cost-method Investments [Line Items]
Long-term purchase commitment, amount	244,000,000
Equity Securities
Schedule of Cost-method Investments [Line Items]
Cash dividends from subsidiaries	$ 15,000,000	$ 10,000,000	$ 6,000,000