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Investments (Portion Of Unrealized Gains And Losses On Equity Investments Held) (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Gain (Loss) on Investments [Line Items] |  |  |
Realized investment gains (losses) | $ (3) | $ (76) | $ (41)
Equity and Trading securities [Member] | Net gains (losses) recognized during the period on equity and trading securities [Member] |  |  |
Gain (Loss) on Investments [Line Items] |  |  |
Realized investment gains (losses) | (50) | (2) | (21)
Equity and Trading securities [Member] | Net gains (losses) recognized during the period on equity and trading securities sold during the period [Member] |  |  |
Gain (Loss) on Investments [Line Items] |  |  |
Realized investment gains (losses) | 0 | 0 | (6)
Equity and Trading securities [Member] | Unrealized gains (losses) recognized during the period on equity and trading securities still held at the reporting date [Member] |  |  |
Gain (Loss) on Investments [Line Items] |  |  |
Realized investment gains (losses) | $ (50) | $ (2) | $ (15)

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- Definition Amount of realized gain (loss) on investment. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(3)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1 + Details
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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 Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(9)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(7)(c)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147481800/320-10-50-9 + Details
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