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For financial guarantee insurance contracts, the undiscounted amount of premium revenue expected to be recognized over the term of the contract period.

No definition available.

Name:	ago_FinancialGuaranteeInsuranceContractsFutureExpectedNetEarnedPremiumtobeRecognized
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For financial guarantee insurance contracts, the amount of premium revenue expected to be recognized beyond the twentieth year following the statement of financial position reporting date.

No definition available.

Name:	ago_FinancialGuaranteeInsuranceContractsFutureExpectedPremiumRevenuetobeRecognizedBeyondYear20
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For financial guarantee insurance contracts, the aggregate amount of premium related to the premium receivable which is expected to be collected beyond the twentieth year following the statement of financial position reporting date.

No definition available.

Name:	ago_FinancialGuaranteeInsuranceContractsPremiumReceivablePremiumExpectedtobeCollectedBeyondYear20
Namespace Prefix:	ago_
Data Type:	xbrli:monetaryItemType
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Amount of unearned premium revenue in the statement of financial position for financial guaranty insurance contracts, net of the unexpired portion of premiums ceded and before adjustment for loss claims paid but not yet expensed.

No definition available.

Name:	ago_FinancialGuaranteeInsuranceContractsUnearnedPremiumRevenueExcludingClaimsPaidNotYetExpensedNet
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Future Net Premiums to be Earned

No definition available.

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Future Premiums to be Collected

No definition available.

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Data Type:	xbrli:stringItemType
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Amount of premium revenue under financial guarantee insurance contract to be recognized in fourth fiscal quarter following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
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Amount of premium revenue under financial guarantee insurance contract to be recognized in eleventh through fifteenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of premium revenue under financial guarantee insurance contract to be recognized in sixteenth through twentieth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of premium revenue under financial guarantee insurance contract to be recognized in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of premium revenue under financial guarantee insurance contract to be recognized in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of premium revenue under financial guarantee insurance contract to be recognized in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of premium revenue under financial guarantee insurance contract to be recognized in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of premium revenue under financial guarantee insurance contract to be recognized in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of premium receivable under financial guarantee insurance contract to be collected in fourth fiscal quarter following current year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-SubTopic 310
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Amount of premium receivable under financial guarantee insurance contract to be collected in eleventh through fifteenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of premium receivable under financial guarantee insurance contract to be collected in sixteenth through twentieth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Amount of premium receivable under financial guarantee insurance contract to be collected in sixth through tenth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of premium receivable under financial guarantee insurance contract to be collected in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of premium receivable under financial guarantee insurance contract to be collected in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Name:	us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanOneAndWithinTwoYearsFromBalanceSheetDate
Namespace Prefix:	us-gaap_
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Amount of premium receivable under financial guarantee insurance contract to be collected in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Name:	us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanThreeAndWithinFourYearsFromBalanceSheetDate
Namespace Prefix:	us-gaap_
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Amount of premium receivable under financial guarantee insurance contract to be collected in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

Name:	us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanTwoAndWithinThreeYearsFromBalanceSheetDate
Namespace Prefix:	us-gaap_
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Amount of premium receivables under financial guarantee insurance contracts.

No definition available.