Net periodic pension expense for defined benefit plans consisted of the following:
| Year Ended December 31 | ||||||||||||
| 2013 | 2012 | 2011 | ||||||||||
| (In thousands) | ||||||||||||
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Service cost |
$ | 24,360 | $ | 29,549 | $ | 28,828 | ||||||
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Interest cost on benefit obligation |
60,130 | 62,037 | 58,545 | |||||||||
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Expected return on plan assets |
(87,353 | ) | (70,511 | ) | (60,700 | ) | ||||||
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Amortization of prior service credit |
(6,556 | ) | (6,559 | ) | (6,559 | ) | ||||||
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Recognized net actuarial loss |
41,076 | 37,386 | 20,530 | |||||||||
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Net periodic pension expense |
$ | 31,657 | $ | 51,902 | $ | 40,644 | ||||||
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Net other postretirement benefits expense for defined benefit plans consisted of the following:
| Year Ended December 31 | ||||||||||||
| 2013 | 2012 | 2011 | ||||||||||
| (In thousands) | ||||||||||||
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Service cost |
$ | 742 | $ | 668 | $ | 535 | ||||||
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Interest cost on benefit obligation |
2,691 | 3,737 | 3,761 | |||||||||
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Amortization of prior service cost (credit) |
(1,359 | ) | 21 | 107 | ||||||||
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Recognized net actuarial loss |
360 | 530 | 36 | |||||||||
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Net other postretirement benefits expense |
$ | 2,434 | $ | 4,956 | $ | 4,439 | ||||||
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