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Employee benefit plans (Tables) | 3 Months Ended
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Mar. 31, 2012
Employee Benefit Plans [Abstract] |
Schedule of net benefit costs | Components of net periodic benefit cost for the Company's pension and other postretirement benefit plans were as follows:
Three Months Ended March 31, | Pension Benefits | Other Postretirement Benefits
2012 |  | 2011 |  | 2012 |  | 2011 |
| (In thousands)
Components of net periodic benefit cost: |  |  |  |
Service cost | $ | 345 |  | $ | 827 |  | $ | 412 |  | $ | 339 |
Interest cost | 4,554 |  | 4,960 |  | 1,143 |  | 1,189 |
Expected return on assets | (5,886 | ) | (5,700 | ) | (1,244 | ) | (1,218 | )
Amortization of prior service cost (credit) | (21 | ) | 43 |  | (272 | ) | (669 | )
Amortization of net actuarial loss | 1,681 |  | 1,543 |  | 526 |  | 311 |
Amortization of net transition obligation | — |  | — |  | 532 |  | 531 |
Net periodic benefit cost, including amount capitalized | 673 |  | 1,673 |  | 1,097 |  | 483 |
Less amount capitalized | 234 |  | 248 |  | 138 |  | (67 | )
Net periodic benefit cost | $ | 439 |  | $ | 1,425 |  | $ | 959 |  | $ | 550 |

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- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Topic 715 -SubTopic 20 -Publisher FASB -Number -Article -Subparagraph (h) -Name Accounting Standards Codification -Paragraph 1 -Section 50 -URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920 + Details
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