XML 54 R41.htm IDEA: XBRL DOCUMENT
v3.25.3

Outstanding Exposure - Components of BIG Net Par Outstanding (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Schedule of Insured Financial Obligations [Line Items] |  |
Net | $ 274,875 | $ 261,552
Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 263,418 | 250,375
Other structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 10,057 | 9,670
Structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 11,457 | 11,177
BIG |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 11,378 | 10,182
BIG | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 10,525 | 9,286
BIG | Other structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 73 | 77
BIG | Structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 853 | 896
BIG | BIG 1 |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 7,251 | 8,102
BIG | BIG 1 | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 7,078 | 7,998
BIG | BIG 1 | Other structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 0 | 0
BIG | BIG 1 | Structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 173 | 104
BIG | BIG 2 |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 2,897 | 706
BIG | BIG 2 | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 2,851 | 656
BIG | BIG 2 | Other structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 18 | 21
BIG | BIG 2 | Structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 46 | 50
BIG | BIG 3 |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 1,230 | 1,374
BIG | BIG 3 | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 596 | 632
BIG | BIG 3 | Other structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 55 | 56
BIG | BIG 3 | Structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 634 | 742
United States | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 212,091 | 201,175
United States | RMBS |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 1,400 | 1,507
United States | Structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 8,102 | 8,453
United States | BIG | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 3,596 | 2,888
United States | BIG | RMBS |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 780 | 819
United States | BIG | Structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 853 | 896
United States | BIG | BIG 1 | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 2,584 | 2,119
United States | BIG | BIG 1 | RMBS |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 173 | 104
United States | BIG | BIG 2 | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 416 | 137
United States | BIG | BIG 2 | RMBS |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 28 | 29
United States | BIG | BIG 3 | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 596 | 632
United States | BIG | BIG 3 | RMBS |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 579 | 686
Non-U.S. public finance | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 51,327 | 49,200
Non-U.S. public finance | Structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 3,355 | 2,724
Non-U.S. public finance | BIG | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 6,929 | 6,398
Non-U.S. public finance | BIG | Structured finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 0 | 0
Non-U.S. public finance | BIG | BIG 1 | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 4,494 | 5,879
Non-U.S. public finance | BIG | BIG 2 | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | 2,435 | 519
Non-U.S. public finance | BIG | BIG 3 | Public finance |  |
Schedule of Insured Financial Obligations [Line Items] |  |
Net | $ 0 | $ 0

X
- Definition Represents the outstanding principal amounts of the underlying insured obligations for financial guaranty contracts, after netting out ceded contracts. + References No definition available. + Details
Name: | ago_InsuredFinancialObligationsOutstandingPrincipalAmountNet
Namespace Prefix: | ago_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition [Line Items] for Schedule of Insured Financial Obligations [Table] + References No definition available. + Details
Name: | ago_ScheduleofInsuredFinancialObligationsLineItems
Namespace Prefix: | ago_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_UnderlyingAssetClassAxis=ago_PublicFinanceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_UnderlyingAssetClassAxis=ago_OtherStructuredFinanceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_UnderlyingAssetClassAxis=us-gaap_StructuredFinanceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_InternalNoninvestmentGradeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis=ago_InternalNoninvestmentGradeLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis=ago_InternalNoninvestmentGradeLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfInsuredFinancialObligationsWithCreditDeteriorationBySurveillanceCategoryAxis=ago_InternalNoninvestmentGradeLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=country_US
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_UnderlyingAssetClassAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=us-gaap_NonUsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |