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Pension Plans and Other Postretirement Benefit Plans - Additional Information (Details) - USD ($) $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Apr. 30, 2024 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Payment for pension benefits |  |  | $ 10 |  | $ 10 |  | $ 42
Settlement loss |  |  |  |  |  |  | $ 12
Curtailment associated gain (loss) |  | $ 1 |  |  |  |  |
Percentage of service related net periodic benefit costs capitalized to utility property |  |  | 45.00% |  |  |  |
Percentage of service related net periodic benefit costs recorded to operating expenses |  |  | 55.00% |  |  |  |
Partial Settlement of Plan [Member] |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Regulatory asset amortization period |  |  |  |  |  |  | 12 years
Deferred Compensation, Excluding Share-based Payments and Retirement Benefits [Member] | Executive Officer [Member] |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Deferred compensation, earlier of retirement, termination, disability or death, percent |  |  | 75.00% |  |  |  |
Deferred compensation incentive payments, percent |  |  | 100.00% |  |  |  |
Equity Securities |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Target investment allocation |  |  | 55.00% |  |  |  |
Debt Securities |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Target investment allocation |  |  | 40.00% |  |  |  |
Real estate |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Target investment allocation |  |  | 5.00% |  |  |  |
Pension Plans, Defined Benefit [Member] |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Expected contributions to pension plan |  |  | $ 10 |  |  |  |
Settlement loss | [1] |  |  |  |  |  | $ 12
Regulatory asset amortization period |  |  |  |  |  |  | 12 years
Curtailment associated gain (loss) |  |  | (1) |  |  |  |
Fair value of plan assets |  |  | 608 | [2] | 590 | [2] | $ 541
Other Postretirement Benefits [Member] |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Expected contributions to pension plan |  |  | 7 |  |  |  |
Fair value of plan assets |  |  | $ 67 | [2] | $ 58 | [2] | $ 49
Other Postretirement Benefits [Member] | Equity Securities |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Target investment allocation |  |  | 60.00% |  | 60.00% |  |
Other Postretirement Benefits [Member] | Debt Securities |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Target investment allocation |  |  | 40.00% |  | 40.00% |  |
Other Postretirement Benefits [Member] | Balanced Mutual Funds [Member] |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Fair value of plan assets |  |  | $ 67 |  | $ 58 |  |
[1] | 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."
[2] | As of December 31, 2024, the SERP had a projected benefit obligation of $27 million and an accumulated benefit obligation of $26 million, with no plan assets.

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