Name:	ago_DividendPaymentRestrictionsScheduleAmountOfStatutoryCapital
Namespace Prefix:	ago_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The maximum percentage of statutory capital that may be paid out as dividends without prior approval from a regulatory agency.

No definition available.

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

The maximum percentage of statutory capital and surplus that may be paid out as dividends without prior approval from a regulatory agency.

No definition available.

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

Represents the period prior to dividend payment by which the entity is required to file an affidavit stating that it will continue to meet required margins, in order to make dividend payments more than the prescribed percentage.

No definition available.

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

Period in Which No Dividends Would Be Paid

No definition available.

Name:	ago_PeriodInWhichNoDividendsWouldBePaid
Namespace Prefix:	ago_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the minimum relevant assets required to be maintained under prescribed or permitted statutory accounting practices, expressed as a percentage of relevant liabilities.

No definition available.

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

The amount of dividends that may be paid or declared in any calendar year without prior approval of regulatory agencies.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(e))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph e

-Article 4

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

Amount of dividends distributed to shareholders in the current accounting period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 50

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6483535&loc=d3e16392-158451

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 60

-Paragraph 60

-Subparagraph h(3)

-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.