| Schedule of Components of Net Periodic Benefit Expense |
The table that follows provides the components of net periodic benefit expense for the three-month and six-month periods ended June 30, 2025 and 2024. | | | | | | | | | | | | | | | | | | | | | | | | | Three Months Ended June 30, | | Pension Benefits | | Other Postretirement Benefits | | (Thousands of dollars) | 2025 | | 2024 | | 2025 | | 2024 | | Service cost | $ | 1,683 | | | $ | 1,706 | | | $ | 84 | | | $ | 135 | | | Interest cost | 8,482 | | | 8,393 | | | 708 | | | 782 | | | Expected return on plan assets | (8,953) | | | (8,359) | | | — | | | — | | | Estimated defined contribution provision | 62 | | | 54 | | | — | | | — | | | Amortization of prior service cost (credit) | 492 | | | 579 | | | (133) | | | (133) | | | Recognized actuarial loss (gain) | 1,914 | | | 2,361 | | | (1,057) | | | (812) | | | | | | | | | | | | | | | | | | | | | | | | | | | Total net periodic benefit expense | $ | 3,680 | | | $ | 4,734 | | | $ | (398) | | | $ | (28) | | | | | | | | | | | Six Months Ended June 30, | | Pension Benefits | | Other Postretirement Benefits | | (Thousands of dollars) | 2025 | | 2024 | | 2025 | | 2024 | | Service cost | $ | 3,366 | | | $ | 3,412 | | | $ | 168 | | | $ | 270 | | | Interest cost | 16,880 | | | 16,784 | | | 1,416 | | | 1,564 | | | Expected return on plan assets | (17,824) | | | (16,716) | | | — | | | — | | | Estimated defined contribution provision | 122 | | | 109 | | | — | | | — | | | Amortization of prior service cost (credit) | 983 | | | 1,158 | | | (266) | | | (266) | | | Recognized actuarial loss (gain) | 3,805 | | | 4,721 | | | (2,113) | | | (1,624) | | | Total net periodic benefit expense | $ | 7,332 | | | $ | 9,468 | | | $ | (795) | | | $ | (56) | | | | | | | | | | | | | | | | | | | | | | | | | |
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