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Pension Plans and Other Postretirement Benefit Plans - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Settlement loss |  |  |  | $ 12
Pension Plans, Defined Benefit [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost | [1] | $ 16 | $ 14 | 24
Interest cost |  | 34 | 33 | 27
Expected return on plan assets |  | $ (45) | $ (44) | $ (44)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] |  | Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax | Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax | Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax
Amortization of prior service cost (Credit) |  |  | $ 1 |
Net loss recognition |  | $ 2 | 5 | $ 4
Settlement loss | [2] |  |  | 12
Net periodic benefit cost |  | 7 | 9 | 23
Other Postretirement Benefits [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Service cost | [1] | 3 | 2 | 4
Interest cost |  | 7 | 7 | 6
Expected return on plan assets |  | $ (4) | $ (3) | $ (3)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] |  | Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax | Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax | Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax
Amortization of prior service cost (Credit) |  | $ (1) | $ (1) | $ (1)
Net loss recognition |  |  |  | 3
Net periodic benefit cost |  | $ 5 | $ 5 | $ 9
[1] | Total service cost in the table above is recorded to the same accounts as labor expense. Labor and benefits expense is recorded to variou s projects based on whether the work is a capital project or an operating expense. Approximately 45 percent of all labor and benefits is capitalized to utility property and 55 percent is expensed to utility other operating expenses.
[2] | The settlement loss was deferred as a regulatory asset and is being amortized over 12 years in accordance with regulatory accounting orders. Pension costs other than service costs are presented in the Consolidated Statements of Income in the line item "Other income-net."

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- Definition Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit 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 45 -Paragraph 3A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480535/715-20-45-3A Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-18 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (h)(5) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(5) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-6 + Details
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- Definition Amount of cost recognized for passage of time related to defined benefit 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 45 -Paragraph 3A -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480535/715-20-45-3A Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-18 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (h)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-6 + Details
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