Line of Credit Facility, Maximum Borrowing Duration

No definition available.

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Namespace Prefix:	ago_
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Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.

+ References

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+ Details

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

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

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Balance Type:	debit
Period Type:	duration

- Details

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- Details

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- Details

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- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
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- Details

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- Details

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- Details

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Long-Term Debt and Credit Facilities - Narrative (Details) - USD ($) $ in Millions				6 Months Ended
	Mar. 14, 2022	Feb. 03, 2022	May 26, 2021	Jun. 30, 2022	Jun. 30, 2021
Debt Instrument [Line Items]
Borrowings under credit facilities				$ 1	$ 0
Senior Notes 3.15 Percent \| Senior Notes \| AGUS
Debt Instrument [Line Items]
Interest rate of debt (as a percent)			3.15%
Debt instrument, face amount			$ 500
Net proceeds from issuance of debt			$ 494
One Month \| Letter of Credit \| Short Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 550
Maximum borrowing duration		1 month
Borrowings under credit facilities	$ 400
One Month \| Letter of Credit \| Short Term Loan Facility \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate
Debt Instrument [Line Items]
Basis spread on variable rate		1.10%
6 Months \| Letter of Credit \| Short Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 150
Maximum borrowing duration		6 months
Borrowings under credit facilities	$ 0
Thirty Days \| Letter of Credit \| Short Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing duration	30 days	30 days