Pension Plans and Other Postretirement Benefits - Changes in Level 3 Pension Plan Assets (Details) - Pension Plan - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Change in plan assets:
Beginning balance	$ 5,346	$ 6,677
Ending balance	5,379	5,346
Level 3
Change in plan assets:
Beginning balance	325
Ending balance	290	325
Real estate \| Level 3
Change in plan assets:
Beginning balance	325	378
Actual return on plan assets	(23)	21
Purchases, sales and settlements	(12)	(74)
Transfers out of Level 3	0	0
Ending balance	$ 290	$ 325

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

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ 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
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480482/715-20-55-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Topic 715
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Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
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Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
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-Name Accounting Standards Codification
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-Paragraph 1
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-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

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- Definition

Amount, measured using unobservable input, of increase (decrease) in plan asset of defined benefit plan from purchase, sale and settlement of trade associated with underlying investment.

+ References

+ 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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