Pension and Other Postretirement Employee Benefit Plans - Changes In Level 3 Fair Value Measurements (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Investments classified in level 3 of the valuation hierarchy	$ 22,201	$ 22,013
Transfers into Level 3	536	173
Unrealized gains	415	400
Decrease for settlements	123	59
Level 3
Defined Benefit Plan Disclosure [Line Items]
Investments classified in level 3 of the valuation hierarchy	$ 3,956	$ 3,124

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held.

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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

No definition available.

+ Details

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
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-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480482/715-20-55-17

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+ Details

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- Definition

Amount, measured using unobservable input, of decrease in plan asset of defined benefit plan from settlement of trade associated with underlying investment.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
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-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

+ Details

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan, for assets transferred into (out of) Level 3 of fair value hierarchy. Includes, but is not limited to, transfer due to change in observability of significant inputs.

+ References

+ Details

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- Details

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