Investments (Portion Of Unrealized Gains And Losses On Equity Investments Held) (Detail) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Gain (Loss) on Investments [Line Items] | ||||
| Realized investment gains (losses) | $ 0 | $ (6) | ||
| Equity and Trading securities [Member] | Location, Statement of Income, Balance [Axis]: us-gaap:NetInvestmentIncome | ||||
| Gain (Loss) on Investments [Line Items] | ||||
| Realized investment gains (losses) | $ (7) | $ (16) | (8) | (17) |
| Equity and Trading securities [Member] | Location, Statement of Income, Balance [Axis]: us-gaap:OtherIncome | ||||
| Gain (Loss) on Investments [Line Items] | ||||
| Realized investment gains (losses) | 0 | 1 | 1 | 3 |
| Equity and Trading securities [Member] | Location, Statement of Income, Balance [Axis]: us-gaap:RealizedInvestmentGainsLosses | ||||
| Gain (Loss) on Investments [Line Items] | ||||
| Realized investment gains (losses) | $ (7) | $ (15) | $ (7) | $ (14) |