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Contracts Accounted for as Insurance - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023
Guarantor Obligations [Line Items] |  |
Weighted average risk-free rates for U.S. dollar denominated financial guaranty insurance obligations | 4.38% | 4.15%
Gross | $ 416,463 | $ 398,037
Gross Exposure | 4,500 |
Ceded Business |  |
Guarantor Obligations [Line Items] |  |
Insured financial obligations insured contractual payments outstanding, amount represented | $ 497 |
Insured financial obligations insured contractual payments outstanding, percentage represented | 0.10% |
Gross Insured Specialty and Reinsurance Business |  |
Guarantor Obligations [Line Items] |  |
Insured financial obligations insured contractual payments outstanding, amount represented | $ 383 |
Minimum |  |
Guarantor Obligations [Line Items] |  |
Risk free discount rate | 1.98% | 1.90%
Maximum |  |
Guarantor Obligations [Line Items] |  |
Risk free discount rate | 5.22% | 5.40%
Premiums Receivable | Foreign Currency Concentration Risk | Premiums Receivable |  |
Guarantor Obligations [Line Items] |  |
Percentage of installment premiums denominated in currencies other than the U.S. dollar | 69.00% | 70.00%

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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 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-21 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-20 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-18 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482861/275-10-50-20 + Details
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