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Contracts Accounted for as Credit Derivatives - Credit Derivatives Subordination and Ratings (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Credit Derivatives
Estimated remaining weighted average life of credit derivatives (in years)	12 years 7 months 6 days	12 years 9 months 18 days
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	$ 3,262	$ 3,203
Net Fair Value Asset (Liability)	(148)	(162)
Expected loss to be recovered	3	3
Public finance | United States
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,211	1,175
Net Fair Value Asset (Liability)	(73)	(79)
Public finance | Non United States
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	1,589	1,565
Net Fair Value Asset (Liability)	(54)	(58)
Structured finance | United States
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	339	342
Net Fair Value Asset (Liability)	(18)	(22)
Structured finance | Non United States
Net Par Outstanding on Credit Derivatives
Net Par Outstanding	123	121
Net Fair Value Asset (Liability)	$ (3)	$ (3)

X

- Definition

Expected Loss on Credit Derivative to Be Paid (Recovered), Including Representation and Warranty Liability (Benefit)

+ References

No definition available.

+ Details

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- References

No definition available.

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- Definition

Represents the outstanding principal amounts of the underlying insured obligations that are accounted for as credit derivatives, net of protection purchased.

+ References

No definition available.

+ Details

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X

- Definition

Average period covered by credit risk derivative contracts, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4K
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5708775-113959

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- 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.

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- Definition

Fair value of credit risk derivative asset after deduction of credit risk derivative liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4K
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=125515794&loc=SL5708775-113959

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