| 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, 2024 and 2023. | | | | | | | | | | | | | | | | | | | | | | | | | Three Months Ended June 30, | | Pension Benefits | | Other Postretirement Benefits | | (Thousands of dollars) | 2024 | | 2023 | | 2024 | | 2023 | | Service cost | $ | 1,706 | | | $ | 1,650 | | | $ | 135 | | | $ | 132 | | | Interest cost | 8,393 | | | 8,564 | | | 782 | | | 874 | | | Expected return on plan assets | (8,359) | | | (8,254) | | | – | | | – | | | Estimated defined contribution provision | 54 | | | 54 | | | – | | | – | | | Amortization of prior service cost (credit) | 579 | | | 155 | | | (133) | | | (133) | | | Recognized actuarial loss (gain) | 2,361 | | | 2,414 | | | (812) | | | (767) | | | | | | | | | | | | | | | | | | | | | | | | | | | Total net periodic benefit expense | $ | 4,734 | | | $ | 4,583 | | | $ | (28) | | | $ | 106 | | | | | | | | | | | Six Months Ended June 30, | | Pension Benefits | | Other Postretirement Benefits | | (Thousands of dollars) | 2024 | | 2023 | | 2024 | | 2023 | | Service cost | $ | 3,412 | | | $ | 3,300 | | | $ | 270 | | | $ | 264 | | | Interest cost | 16,784 | | | 17,071 | | | 1,564 | | | 1,748 | | | Expected return on plan assets | (16,716) | | | (16,448) | | | – | | | – | | | Estimated defined contribution provision | 109 | | | 108 | | | – | | | – | | | Amortization of prior service cost (credit) | 1,158 | | | 310 | | | (266) | | | (266) | | | Recognized actuarial loss (gain) | 4,721 | | | 4,815 | | | (1,624) | | | (1,548) | | | Total net periodic benefit expense | $ | 9,468 | | | $ | 9,156 | | | $ | (56) | | | $ | 198 | | | | | | | | | | | | | | | | | | | | | | | | | |
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