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Employee Retirement Benefits - Components of Net Periodic Costs for Qualified and Supplemental Pension Plans (Details) - Qualified Pension Plans - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Defined Benefit Plan Disclosure |  |  |  |
Service cost | $ 2 | $ 1 | $ 4 | $ 4
Interest cost | 3 | 4 | 10 | 10
Expected return on plan assets | (6) | (5) | (17) | (16)
Amortization of actuarial (gain) loss and prior service cost | 0 | 0 | (2) | 1
Total non-service benefit | (3) | (1) | (9) | (5)
Net periodic benefit cost | $ (1) | $ 0 | $ (5) | $ (1)

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