Retirement Plans and Postretirement Benefits The components of our consolidated net pension costs are set forth in the following table: | | | | | | | | | | | | | | | | | | For the Three Months Ended September 30, | | For the Nine Months Ended September 30, | | 2018 | | 2017 | | 2018 | | 2017 | | (Dollars in thousands) | Service cost | $ | 498 |
| | $ | 496 |
| | $ | 1,494 |
| | $ | 1,487 |
| Interest cost | 1,239 |
| | 1,385 |
| | 3,721 |
| | 4,154 |
| Expected return on plan assets | (1,502 | ) | | (1,389 | ) | | (4,506 | ) | | (4,166 | ) | Net cost | $ | 235 |
| | $ | 492 |
| | $ | 709 |
| | $ | 1,475 |
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The components of our consolidated net postretirement costs are set forth in the following table: | | | | | | | | | | | | | | | | | | For the Three Months Ended September 30, | | For the Nine Months Ended September 30, | | 2018 | | 2017 | | 2018 | | 2017 | | (Dollars in thousands) | Service cost | $ | 3 |
| | $ | 1 |
| | $ | 3 |
| | $ | 1 |
| Interest cost | 229 |
| | 241 |
| | 731 |
| | 724 |
| Net cost | $ | 232 |
| | $ | 242 |
| | $ | 734 |
| | $ | 725 |
|
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