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

Represents the reserve for losses and loss adjustment expenses, net of reinsurance recoverable on unpaid losses and net of salvage and subrogation recoverable.

No definition available.

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

Represents the effect on reserve for losses and loss adjustment expenses, net of reinsurance recoverable on unpaid losses and net of salvage and subrogation recoverable related to consolidating VIEs.

No definition available.

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

Represents the reserve for losses and loss adjustment expenses, net of reinsurance recoverable on unpaid losses, net of salvage and subrogation recoverable and before adjusting for the effect of consolidating VIEs.

No definition available.

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

Alternate concept name for the aggregate amount of policy reserves (provided for future obligations including unpaid claims and claims adjustment expenses) and policy benefits (liability for future policy benefits) as of the balance sheet date, net of reinsurance recoverable on unpaid losses and before adjusting for the effect of consolidating VIEs.

No definition available.

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

Represents the aggregate amount of policy reserves (provided for future obligations including unpaid claims and claims adjustment expenses) and policy benefits (liability for future policy benefits) as of the balance sheet date; grouped amount of all the liabilities associated with the company's net of reinsurance policies.

No definition available.

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

Represents the net of assets and liability value when the expected salvage and subrogation exceeds the estimated loss reserve for a policy, for ceded contracts.

No definition available.

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

Represents the effect on the salvage and subrogation recoverable related to consolidating VIEs.

No definition available.

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

The estimated amount as of the balance sheet date to be received by an insurer from the sale of property (usually damaged) on which the insurer has paid a total claim to the insured and has obtained title to the property and the right of an insurer to pursue any course of recovery of damages, in its name or in the name of the policyholder, against a third party who is liable for costs relating to an insured event that have been paid by the insurer, before adjusting for the effect of consolidating VIEs.

No definition available.