Name:	ago_ConsolidatedComplaintsFiledNumberOfPlaintiffs
Namespace Prefix:	ago_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the amount of the underlying obligation insured by financial guarantors including the entity, which is the subject matter of a putative class action.

No definition available.

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

Represents the minimum number of proceedings for recoveries of losses, or failure to obtain recoveries, to have a material impact on the entity's results of operations in a particular quarter or fiscal year.

No definition available.

Name:	ago_MinimumNumberOfProceedingsForRecoveriesToHavePotentialMaterialImpact
Namespace Prefix:	ago_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the number of non-class action lawsuits for which the entity requested dismissal and the dismissal was denied by the court.

No definition available.

Name:	ago_NonClassActionLawsuitsNumberDismissalDenied
Namespace Prefix:	ago_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents number of commutations disputed.

No definition available.

Name:	ago_NumberOfCommutations
Namespace Prefix:	ago_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the number of credit derivative transactions which the entity has improperly terminated as per the allegations of the complainants.

No definition available.

Name:	ago_NumberOfCreditDerivativeTransactionsAllegedToBeImproperlyTerminated
Namespace Prefix:	ago_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Represents the number of credit derivative transactions for which the entity has improperly calculated the termination payment as per the allegations of the complainants.

No definition available.

Name:	ago_NumberOfCreditDerivativeTransactionsForWhichTerminationPaymentAllegedToBeImproperlyCalculated
Namespace Prefix:	ago_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Represents the number of non-class action lawsuits filed naming the entity among other defendants.

No definition available.

Name:	ago_NumberOfNonClassActionLawsuits
Namespace Prefix:	ago_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the number of putative class action lawsuits that were filed in a federal court alleging federal antitrust violations in the municipal derivatives industry.

No definition available.

Name:	ago_NumberOfPutativeClassActionLawsuitsFiled
Namespace Prefix:	ago_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the amount of payment on the termination of credit derivatives transactions which the complainant owes to defendant as per the calculation of defendant.

No definition available.

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

Represents the amount of payment on the termination of credit derivatives transactions which the defendant owes to complainant as per the calculation of complainant.

No definition available.

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

Represents the percentage of amount in segregated account payable in cash.

No definition available.

Name:	ago_PercentageOfSegregatedAccountPayableInCash
Namespace Prefix:	ago_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of amount in segregated account payable in surplus notes issued.

No definition available.

Name:	ago_PercentageOfSegregatedAccountPayableInNotesIssued
Namespace Prefix:	ago_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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Data Type:	xbrli:stringItemType
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Period Type:	duration

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

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Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

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