Name:	ago_ConditionalDefaultRateIntermediateStressPeriod
Namespace Prefix:	ago_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

Represents the period for which estimated default rates for a pool of insured obligations are calculated.

No definition available.

Name:	ago_DefaultEstimateLiquidationPeriod
Namespace Prefix:	ago_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

Represents the final conditional default rate on a pool of insured obligations as a percentage of the plateau conditional default rate.

No definition available.

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

Represents the intermediate conditional default rate on a pool of insured obligations as a percentage of the plateau conditional default rate.

No definition available.

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

The period for which the intermediate conditional default rate on a pool of insured obligations is held constant.

No definition available.

Name:	ago_IntermediateConditionalDefaultRateConstantPeriod
Namespace Prefix:	ago_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

Represents the intermediate conditional default rate on a pool of insured obligations in base case scenarios when such insured obligations are considered as stress cases.

No definition available.

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

Represents the liquidation rate used to estimate the number of insured obligations in the 30 - 59 days delinquent loan category that will default.

No definition available.

Name:	ago_LiquidationRateFor30To59DaysDelinquentCategory
Namespace Prefix:	ago_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the liquidation rate used to estimate the number of insured obligations in the 60 - 89 days delinquent loan category that will default.

No definition available.

Name:	ago_LiquidationRateFor60To89DaysDelinquentCategory
Namespace Prefix:	ago_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the liquidation rate used to estimate the number of insured obligations in the 90 or more days delinquent loan category that will default.

No definition available.

Name:	ago_LiquidationRateFor90OrMoreDaysDelinquentCategory
Namespace Prefix:	ago_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the liquidation rate used to estimate the number of insured obligations in the bankruptcy delinquent loan category that will default.

No definition available.

Name:	ago_LiquidationRateForBankruptcyDelinquentCategory
Namespace Prefix:	ago_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the liquidation rate used to estimate the number of insured obligations in foreclosure that will default.

No definition available.

Name:	ago_LiquidationRateForForeclosureCategory
Namespace Prefix:	ago_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the liquidation rate used to estimate the number of insured obligations related to real estate owned by the entity that will default.

No definition available.

Name:	ago_LiquidationRateForRealEstateOwnedCategory
Namespace Prefix:	ago_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the minimum amount of mortgage-backed and asset-backed securities included in the loan-level data under the Loan Performance securities databases.

No definition available.

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

The minimum percentage of the market represented by the mortgage-backed and asset-backed securities included in the loan-level data under the Loan Performance securities databases.

No definition available.

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

Represents the present value of the final level of assumed lifetime losses on a pool of insured obligations as a percentage of principal balance.

No definition available.

Name:	ago_LossSeverityFinal
Namespace Prefix:	ago_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the period over which the loss severity is assumed to decline to a final level.

No definition available.

Name:	ago_LossSeverityRecoveryPeriod
Namespace Prefix:	ago_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

Represents the minimum percentage of mortgage loans originally included in the pool of insured obligations with an option to make a minimum payment that has the potential to negatively amortize the loan required to categorize a transaction as an Option ARM.

No definition available.

Name:	ago_MinimumPercentageOfLoansWithPotentialNegativeAmortizationForOptionARMCategory
Namespace Prefix:	ago_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the period after which defaults projected to occur on a pool of insured obligations represent defaults that can be attributed to obligations that are currently performing.

No definition available.

Name:	ago_PeriodBeforeDefaultsInPerformingBorrowersCategory
Namespace Prefix:	ago_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

Represents the period over which the application of the constant conditional default rate would produce approximately the amount of defaults calculated for each delinquency category of insured financial obligations.

No definition available.

Name:	ago_PeriodForApplicationOfConstantConditionalDefaultRate
Namespace Prefix:	ago_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

Represents the period over which defaults projected to occur on a pool of insured obligations represent defaults that can be attributed to obligations that are currently delinquent or in foreclosure.

No definition available.