Name:	ago_FinancialGuaranteeInsuranceContractsPremiumReceivablePremiumExpectedtobeCollectedBeyondYear20
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Represents the cash collected against the premiums for financial guaranty insurance contracts of variable interest entity.

No definition available.

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

[Line Items] for Financial Guarantee Insurance Premiums [Table]

No definition available.

Name:	ago_FinancialGuaranteeInsurancePremiumsLineItems
Namespace Prefix:	ago_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

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
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 50
-Paragraph 3
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 50
-Paragraph 3
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290

Name:	us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThan10AndWithin15YearsFromBalanceSheetDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

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
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 50
-Paragraph 3
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 50
-Paragraph 3
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=6933075&loc=SL5748726-161290

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

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).

Name:	us-gaap_FinancialGuaranteeInsuranceContractsPremiumExpectedToBeCollectedMoreThanFourAndWithinFiveYearsFromBalanceSheetDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

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_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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_
Data Type:	xbrli:monetaryItemType
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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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Period Type:	instant

Amount of premium receivables under financial guarantee insurance contracts.

No definition available.