Name:	ago_GainContingencyAllegationsPaymentForTerminationofCreditDerivativeTransactionsOwedbyDefendanttoPlaintiffAsPerCalculationofPlaintiff
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Data Type:	xbrli:monetaryItemType
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Represents the amount of payment on the termination of credit derivatives transactions which the plaintiff owes to defendant as per the calculation of defendant.

No definition available.

Name:	ago_GainContingencyAllegationsPaymentForTerminationofCreditDerivativeTransactionsOwedbyPlaintifftoDefendantAsPerCalculationofDefendant
Namespace Prefix:	ago_
Data Type:	xbrli:monetaryItemType
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Represents the number of credit derivative transactions which the entity has improperly terminated as per the allegations of the plaintiff.

No definition available.

Name:	ago_LossContingencyCreditDerivativeTransactionImproperlyTerminatedAsPerTheAllegationsOfThePlaintiffNumber
Namespace Prefix:	ago_
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Represents the number of credit derivative transactions which the entity has improperly calculated termination payment as per the allegations of the plaintiff.

No definition available.

Name:	ago_LossContingencyCreditDerivativeTransactionsImproperlyCalculatedTerminationPaymentAsPerTheAllegationsOfThePlaintiffNumber
Namespace Prefix:	ago_
Data Type:	xbrli:integerItemType
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Operating Leases, Rented Area

No definition available.

Name:	ago_OperatingLeasesRentedArea
Namespace Prefix:	ago_
Data Type:	num:areaItemType
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The amount or range of possible amounts of gain that could be realized upon the resolution of a contingency.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6397426&loc=d3e17499-108355

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Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

No definition available.

Name:	us-gaap_LeaseAndRentalExpense
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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980

Name:	us-gaap_LesseeOperatingLeaseRenewalTerm
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Data Type:	xbrli:durationItemType
Balance Type:	na
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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.

No definition available.

Name:	us-gaap_LossContingenciesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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Period Type:	duration

Name:	dei_LegalEntityAxis=ago_AssuredGuarantyMunicipalCorpMember
Namespace Prefix:
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Name:	dei_LegalEntityAxis=ago_AssuredGuarantyFinancialProductsIncMember
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Data Type:	na
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Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=us-gaap_GuaranteeObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	dei_LegalEntityAxis=ago_LehmanBrothersInternationalEuropeMember
Namespace Prefix:
Data Type:	na
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Name:	us-gaap_GainContingenciesByNatureAxis=us-gaap_PositiveOutcomeOfLitigationMember
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Name:	us-gaap_LitigationStatusAxis=us-gaap_PendingLitigationMember
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Name:	srt_RangeAxis=srt_MinimumMember
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