XML 74 R54.htm IDEA: XBRL DOCUMENT v3.22.1

Expected Loss to be Paid (Recovered) - Net Economic Loss Development (Benefit) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Schedule of Expected Losses to be Paid [Line Items]
Net Economic Loss Development (Benefit)	$ (44)	$ 13
RMBS | UNITED STATES
Schedule of Expected Losses to be Paid [Line Items]
Net Economic Loss Development (Benefit)	7	11
RMBS | UNITED STATES | First Lien
Schedule of Expected Losses to be Paid [Line Items]
Net Economic Loss Development (Benefit)	18	25
RMBS | UNITED STATES | Second Lien
Schedule of Expected Losses to be Paid [Line Items]
Net Economic Loss Development (Benefit)	$ (11)	$ (14)

X

- Definition

Guarantor Obligations, Net Expected Loss Development After Recoveries for Representations and Warranties

+ References

No definition available.

+ Details

Name:	ago_GuarantorObligationsNetExpectedLossDevelopmentAfterRecoveriesforRepresentationsandWarranties
Namespace Prefix:	ago_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

[Line Items] for Schedule of Expected Losses to be Paid [Table]

+ References

No definition available.

+ Details

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

X

- Details

Name:	us-gaap_UnderlyingAssetClassAxis=us-gaap_ResidentialMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_StatementGeographicalAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis=us-gaap_FirstMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionLoanCategoryAxis=us-gaap_SecondMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: