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

Represents the bank profit expressed as a percentage of original or gross spread.

No definition available.

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

Represents the rate at which expected future cash flows from credit derivatives are discounted.

No definition available.

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

Represents the gross spread allocated to hedge cost. Hedge cost represents the cost of protection purchased on the entity by the originator to hedge their counterparty credit risk exposure to the entity.

No definition available.

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

Represents the hedge cost expressed as a percentage of original or gross spread.

No definition available.

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

Represents the number of sources on which credit spread is based.

No definition available.

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

Represents the original gross spread/cash bond price. Gross spread is the difference between the yield of a security paid by an issuer on an insured versus uninsured basis or in the case of a CDS transaction the difference between the yield and an index such as LIBOR.

No definition available.

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

Represents the percentage of gross spread.

No definition available.

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

Represents the percentage of exposure hedged by the bank or deal originator.

No definition available.

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

Represents the gross spread allocated to net spread. It represents the premiums received by the company for the credit protection provided. Such net spread varies based on the variation in the gross spread, bank profit and hedged cost.

No definition available.

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

Represents the premiums received per annum by the company expressed as a percentage of original or gross spread.

No definition available.

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

Represents the number of securities for which prices provided by a third party pricing service are adjusted based on the entity's own cash flow analysis.

No definition available.

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

Represents the percentage of fixed maturity securities which have been valued using model processes set by the entity to the company's fixed-income securities and short-term investments which are valued at fair value.

No definition available.

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

Represents the number of fixed maturity securities which have been valued using model processes set by the entity.

No definition available.

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

Represents the percentage of CDS contracts which are fair valued using minimum premium. Minimum premium is the minimum rate that the company would currently charge to assume similar risks.

No definition available.

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

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6379932&loc=d3e22054-111558

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Available-for-Sale Securities

-URI http://asc.fasb.org/extlink&oid=6505594