The following table provides the components of net periodic benefit cost for the second quarters and six months ended June 30, 2014 and 2013. | | | | | | | | | | | | | | | | | | Pension Benefits | | OPEB | | Quarter Ended | | Quarter Ended | | June 30 | | June 30 | | 2014 | | 2013 | | 2014 | | 2013 | Service cost | $ | — |
| | $ | — |
| | $ | 153 |
| | $ | 224 |
| Interest cost | 1,550 |
| | 1,335 |
| | 374 |
| | 349 |
| Expected return on plan assets | (2,580 | ) | | (2,307 | ) | | — |
| | — |
| Amortization of: | | | | | | | | Unrecognized actuarial net loss | 430 |
| | 598 |
| | 21 |
| | 45 |
| Unrecognized prior service credit | — |
| | — |
| | (286 | ) | | (111 | ) | Curtailment | — |
| | — |
| | — |
| | (116 | ) | Net periodic benefit cost (credit) | $ | (600 | ) | | $ | (374 | ) | | $ | 262 |
| | $ | 391 |
|
| | | | | | | | | | | | | | | | | | Pension Benefits | | OPEB | | Six Months Ended | | Six Months Ended | | June 30 | | June 30 | | 2014 | | 2013 | | 2014 | | 2013 | Service cost | $ | — |
| | $ | — |
| | $ | 306 |
| | $ | 473 |
| Interest cost | 3,101 |
| | 2,670 |
| | 749 |
| | 711 |
| Expected return on plan assets | (5,161 | ) | | (4,614 | ) | | — |
| | — |
| Amortization of: | | | | | | | | Unrecognized actuarial net loss | 859 |
| | 1,196 |
| | 43 |
| | 103 |
| Unrecognized prior service credit | — |
| | — |
| | (573 | ) | | (174 | ) | Curtailment | — |
| | — |
| | — |
| | (116 | ) | Net periodic benefit cost (credit) | $ | (1,201 | ) | | $ | (748 | ) | | $ | 525 |
| | $ | 997 |
|
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