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Contracts Accounted for as Credit Derivatives - Distribution of Credit Derivative Net Par Outstanding by Internal Rating (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Credit Derivatives
Net Par Outstanding	$ 3,489	$ 3,203
BIG
Credit Derivatives
Net Par Outstanding	55	57
Credit Concentration Risk | Derivative, Aggregate Notional Amount
Credit Derivatives
Net Par Outstanding	$ 3,489	$ 3,203
Percentage of installment premiums denominated in currencies other than the U.S. dollar	100.00%	100.00%
Credit Concentration Risk | Derivative, Aggregate Notional Amount | AAA
Credit Derivatives
Net Par Outstanding	$ 1,255	$ 1,260
Percentage of installment premiums denominated in currencies other than the U.S. dollar	36.00%	39.30%
Credit Concentration Risk | Derivative, Aggregate Notional Amount | AA
Credit Derivatives
Net Par Outstanding	$ 1,020	$ 1,064
Percentage of installment premiums denominated in currencies other than the U.S. dollar	29.20%	33.20%
Credit Concentration Risk | Derivative, Aggregate Notional Amount | A
Credit Derivatives
Net Par Outstanding	$ 689	$ 232
Percentage of installment premiums denominated in currencies other than the U.S. dollar	19.70%	7.20%
Credit Concentration Risk | Derivative, Aggregate Notional Amount | BBB
Credit Derivatives
Net Par Outstanding	$ 470	$ 590
Percentage of installment premiums denominated in currencies other than the U.S. dollar	13.50%	18.50%
Credit Concentration Risk | Derivative, Aggregate Notional Amount | BIG
Credit Derivatives
Net Par Outstanding	$ 55	$ 57
Percentage of installment premiums denominated in currencies other than the U.S. dollar	1.60%	1.80%

X

- 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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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482810/280-10-50-42

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 825
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-Section 50
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-Publisher FASB
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 825
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 275
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 275
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-Paragraph 20
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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.

+ Details

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