Loss and Loss Adjustment Expense Reserves (Schedule of Loss and Loss Adjustment Expenses Reserves) (Detail) - USD ($) $ in Millions |
9 Months Ended | |||||
|---|---|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
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| Loss And Loss Adjustment Expense Reserves [Line Items] | ||||||
| Changes in unearned premium revenue | $ (21) | $ (21) | ||||
| Loss And Lae Reserves [Member] | ||||||
| Loss And Loss Adjustment Expense Reserves [Line Items] | ||||||
| Gross loss and LAE reserve, beginning balance | [1] | 454 | ||||
| Loss payments for cases | (90) | |||||
| Accretion of claim liability discount | 13 | |||||
| Changes in discount rates | (24) | |||||
| Changes in assumptions | [2] | 45 | ||||
| Changes in unearned premium revenue | 1 | |||||
| Gross loss and LAE reserve, ending balance | [1] | $ 399 | ||||
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| X | ||||||||||
- Definition Financial Guarantee Insurance Contracts Claim Liability Significant Components Of Change In Assumptions No definition available.
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| X | ||||||||||
- Definition Loss And Loss Adjustment Expense Reserves [Line Items] No definition available.
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| X | ||||||||||
- Definition Loss payments for cases. No definition available.
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| X | ||||||||||
- Definition This element represents the amount of the change in the claim liability related to financial guarantee insurance contracts arising from the accretion of the discount of the claim liability. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition This element represents the amount of change in the claim liability related to financial guarantee insurance contracts arising from a change in the rate used to discount the claim liability. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount of increase (decrease) unearned premiums written. Excludes portion of unearned premiums amortized into income. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Details
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