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Actual Investment Allocations (Detail) | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | --- | --- | ---
Pension Plans |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target Allocation |  |  | 58.00% |  |
Actual Allocation |  |  | 100.00% | 100.00% | 100.00%
Pension Plans | Equity Funds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Actual Allocation |  |  | 57.00% | 53.00% | 57.00%
Pension Plans | Fixed Income Securities |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target Allocation |  |  | 37.00% |  |
Actual Allocation |  |  | 36.00% | 38.00% | 38.00%
Pension Plans | Other |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Actual Allocation | [1] |  | 1.00% | 2.00% | 1.00%
Other Postretirement Benefit Plans, Defined Benefit |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Actual Allocation |  |  | 100.00% | 100.00% | 100.00%
Other Postretirement Benefit Plans, Defined Benefit | Equity Funds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target Allocation |  |  | 55.00% |  |
Actual Allocation |  |  | 56.00% | 55.00% | 56.00%
Other Postretirement Benefit Plans, Defined Benefit | Fixed Income Securities |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target Allocation |  |  | 45.00% |  |
Actual Allocation |  |  | 44.00% | 45.00% | 44.00%
Real Estate Funds | Pension Plans |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target Allocation |  |  | 5.00% |  |
Actual Allocation |  |  | 6.00% | 7.00% | 4.00%
Scenario Forecast | Pension Plans |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target Allocation |  | 5.00% |  |  |
Scenario Forecast | Pension Plans | Equity Funds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target Allocation |  | 58.00% |  |  |
Scenario Forecast | Pension Plans | Fixed Income Securities |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target Allocation |  | 37.00% |  |  |
Scenario Forecast | Other Postretirement Benefit Plans, Defined Benefit | Equity Funds |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target Allocation |  | 55.00% |  |  |
Scenario Forecast | Other Postretirement Benefit Plans, Defined Benefit | Fixed Income Securities |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Target Allocation |  | 45.00% |  |  |
[1] | Represents investments being held in cash equivalents as of December 31, 2023, December 31, 2022 and December 31, 2021 pending payment of benefits.

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- Definition Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + 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 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(i) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480506/715-20-50-1 + Details
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