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Investments (Securities Held In Unrealized Loss Position And Insured By Financial Guarantor) (Detail) - Financial Guarantee [Member] $ in Millions | Sep. 30, 2023 USD ($)
--- | ---
Schedule Of Investments [Line Items] |  |
Fair value | $ 100 |
Unrealized loss | (47) |
Insurance loss reserve | 20 | [1]
Mortgage-backed [Member] |  |
Schedule Of Investments [Line Items] |  |
Fair value | 16 |
Unrealized loss | (5) |
Insurance loss reserve | 20 | [1]
Corporate Obligations [Member] |  |
Schedule Of Investments [Line Items] |  |
Fair value | 77 |
Unrealized loss | (42) |
Insurance loss reserve | 0 | [1]
Other [Member] |  |
Schedule Of Investments [Line Items] |  |
Fair value | 7 |
Unrealized loss | 0 |
Insurance loss reserve | $ 0 | [1]
[1] | Insurance loss reserve estimates are based on the proportion of par value owned to the total amount of par value insured and are discounted using a discount rate equal to the risk-free rate applicable to the currency and weighted average remaining life of the insurance contract and may differ from the fair value.

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- Definition Amount of accumulated pre-tax unrealized losses before deducting pre-tax unrealized gains on investments in available-for-sale securities impacting investments. + References No definition available. + Details
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- Definition The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events by financial guarantor that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date. + References No definition available. + Details
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