v3.25.4

Insurance Company Regulatory Requirements - Narrative (Details) € in Millions, £ in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($)	Mar. 31, 2026 USD ($)	Dec. 31, 2025 GBP (£)	Dec. 31, 2025 USD ($)	Dec. 31, 2025 EUR (€)	Dec. 31, 2024 GBP (£)	Dec. 31, 2024 USD ($)	Dec. 31, 2024 EUR (€)
AGUK
Statutory Accounting Practices [Line Items]
Own funds			£ 461	$ 622		£ 439	$ 549
AGE
Statutory Accounting Practices [Line Items]
Own funds				51	€ 43		$ 36	€ 35
AG (U.S. domiciled) \| Maryland
Statutory Accounting Practices [Line Items]
Threshold for dividend payments as a percentage of policyholder surplus	10.00%
Threshold for dividend payments, percentage of adjusted net investment income	100.00%
Amount available for distribution, current year				245
AG (U.S. domiciled) \| Maryland \| Forecast
Statutory Accounting Practices [Line Items]
Amount available for distribution, next fiscal quarter		$ 29
AG Re \| Bermuda
Statutory Accounting Practices [Line Items]
Amount available for distribution, current year				292
Dividend payment restrictions, percentage of statutory capital	15.00%
Dividend restrictions on statutory capital and surplus (as a percent)	25.00%
Capital distributions	$ 129
Statutory surplus				292
Unencumbered assets				213
Statutory amount available for dividend payments, deficit				312
AGRO \| Bermuda
Statutory Accounting Practices [Line Items]
Amount available for distribution, current year				124
Capital distributions	$ 21
Statutory surplus				124
Unencumbered assets				435
Statutory amount available for dividend payments				$ 359

The maximum amount of statutory capital that may be paid out as dividends without prior approval from a regulatory agency.

+ References

No definition available.

+ Details

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Namespace Prefix:	ago_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The maximum percentage of statutory capital that may be paid out as dividends without prior approval from a regulatory agency.

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

The maximum percentage of statutory capital and surplus that may be paid out as dividends without prior approval from a regulatory agency.

+ References

No definition available.

+ Details

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Namespace Prefix:	ago_
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Balance Type:	na
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- Definition

Dividend Payments Restrictions Schedule, Statutory Surplus

+ References

No definition available.

+ Details

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Namespace Prefix:	ago_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Regulatory Capital Resources Under Solvency II, Own Funds

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Statutory Accounting Practices, Statutory Amount Available for Dividend Payments, Deficit

+ References

No definition available.

+ Details

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Namespace Prefix:	ago_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Statutory Accounting Practices, Statutory Amount Available for Dividend Payments without Regulatory Approval, Quarterly Payment

+ References

No definition available.

+ Details

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Namespace Prefix:	ago_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Statutory Accounting Practices, Statutory Threshold for Dividend Payments, Percentage of Adjusted Net Investment Income

+ References

No definition available.

+ Details

Name:	ago_StatutoryAccountingPracticesStatutoryThresholdforDividendPaymentsPercentageofAdjustedNetInvestmentIncome
Namespace Prefix:	ago_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Statutory Accounting Practices, Statutory Threshold for Dividend Payments, Percentage of Policyholder' Surplus

+ References

No definition available.

+ Details

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Namespace Prefix:	ago_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Unencumbered Assets which are not held in trust for the benefit of cedants.

+ References

No definition available.

+ Details

Name:	ago_UnencumberedAsset
Namespace Prefix:	ago_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477908/944-505-50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477908/944-505-50-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477908/944-505-50-5

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477908/944-505-50-3

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477908/944-505-50-1

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(23)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of dividends available for payment after computation of statutory restrictions on capital surplus.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of dividends that can be declared or paid without approval of regulatory agency.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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ASSURED GUARANTY LTD 10-K