| Components of Net Periodic Costs |
Components of net periodic costs (benefits) for the three and six months ended June 30 are as follows: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pension Benefits | | Other Postretirement Benefits | | Three Months Ended | | Six Months Ended | | Three Months Ended | | Six Months Ended | | June 30, | | June 30, | | June 30, | | June 30, | | 2013 | | 2012 | | 2013 | | 2012 | | 2013 | | 2012 | | 2013 | | 2012 | Service cost | $ | 5,581 |
| | $ | 4,850 |
| | $ | 11,287 |
| | $ | 10,003 |
| | $ | 4,849 |
| | $ | 4,566 |
| | $ | 9,698 |
| | $ | 9,766 |
| Interest cost | 8,909 |
| | 9,415 |
| | 17,752 |
| | 18,793 |
| | 29,619 |
| | 32,795 |
| | 59,237 |
| | 68,322 |
| Expected return on plan assets | (12,711 | ) | | (11,452 | ) | | (24,855 | ) | | (23,079 | ) | | — |
| | — |
| | — |
| | — |
| Amortization of prior service cost (credits) | (407 | ) | | (407 | ) | | (815 | ) | | (815 | ) | | (7,804 | ) | | (13,410 | ) | | (15,608 | ) | | (25,009 | ) | Recognized net actuarial loss | 10,547 |
| | 11,654 |
| | 22,722 |
| | 23,917 |
| | 17,595 |
| | 20,020 |
| | 35,190 |
| | 40,365 |
| Settlement loss | 5,087 |
| | — |
| | 32,202 |
| | — |
| | — |
| | — |
| | — |
| | — |
| Net periodic benefit cost | $ | 17,006 |
| | $ | 14,060 |
| | $ | 58,293 |
| | $ | 28,819 |
| | $ | 44,259 |
| | $ | 43,971 |
| | $ | 88,517 |
| | $ | 93,444 |
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