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Retirement-Related Benefits - All Retirement Plans Cost (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2025 | Mar. 31, 2024
Retirement Benefits [Abstract] |  |
Defined benefit pension and defined contribution pension plans — cost | $ 233 | $ 323
Nonpension postretirement plans — cost | 32 | 30
Total | $ 266 | $ 353
Year-to-year percent change, Defined benefit pension and defined contribution plans — cost (as a percent) | (27.70%) |
Year-to-year percent change, Nonpension postretirement plans — cost (as a percent) | 6.20% |
Year-to-year percent change, Total (as a percent) | (24.80%) |

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- Definition The percentage change, period to period, in the nonpension postretirement plans cost. + References No definition available. + Details
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- Definition Pension and Other Postretirement Benefit (Expense) Change, Period to Period, Percent + References No definition available. + Details
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- Definition Pension Expense Change, Period to Period, Percent + References No definition available. + Details
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- References No definition available. + Details
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- Definition Amount of cost (reversal of cost) for other postretirement benefits. Excludes pension benefits. + References No definition available. + Details
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- Definition Amount of cost (reversal of cost) for pension and other postretirement benefits. + References No definition available. + Details
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- Definition Amount of cost (reversal of cost) for pension benefits. Excludes other postretirement benefits. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 48 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482785/280-10-55-48 + Details
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