The following table provides the components of net periodic benefit cost for the third quarters and nine months ended September 30, 2014 and 2013. | | | | | | | | | | | | | | | | | | Pension Benefits | | OPEB | | Quarter Ended | | Quarter Ended | | September 30 | | September 30 | | 2014 | | 2013 | | 2014 | | 2013 | Service cost | $ | — |
| | $ | — |
| | $ | 153 |
| | $ | 157 |
| Interest cost | 1,551 |
| | 1,335 |
| | 375 |
| | 329 |
| Expected return on plan assets | (2,582 | ) | | (2,307 | ) | | — |
| | — |
| Amortization of: | | | | | | | | Unrecognized actuarial net loss | 430 |
| | 598 |
| | 22 |
| | — |
| Unrecognized prior service credit | — |
| | — |
| | (287 | ) | | (289 | ) | Net periodic benefit cost (credit) | $ | (601 | ) | | $ | (374 | ) | | $ | 263 |
| | $ | 197 |
|
| | | | | | | | | | | | | | | | | | Pension Benefits | | OPEB | | Nine Months Ended | | Nine Months Ended | | September 30 | | September 30 | | 2014 | | 2013 | | 2014 | | 2013 | Service cost | $ | — |
| | $ | — |
| | $ | 459 |
| | $ | 630 |
| Interest cost | 4,652 |
| | 4,005 |
| | 1,124 |
| | 1,040 |
| Expected return on plan assets | (7,743 | ) | | (6,921 | ) | | — |
| | — |
| Amortization of: | | | | | | | | Unrecognized actuarial net loss | 1,289 |
| | 1,794 |
| | 65 |
| | 103 |
| Unrecognized prior service credit | — |
| | — |
| | (860 | ) | | (463 | ) | Curtailment | — |
| | — |
| | — |
| | (116 | ) | Net periodic benefit cost (credit) | $ | (1,802 | ) | | $ | (1,122 | ) | | $ | 788 |
| | $ | 1,194 |
|
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