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Benefit Plans (Tables) | 3 Months Ended
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Mar. 31, 2018
Retirement Benefits [Abstract] |
Components of net periodic benefit cost | Table 10.1 provides the components of net periodic benefit cost for our pension, supplemental executive retirement and other postretirement benefit plans for the three months ended March 31, 2018 and 2017.
| Table | 10.1 |  |  |  |  |  |  |  |
Components of net periodic benefit cost |  |  | Three Months Ended March 31,
|  | Pension and Supplemental Executive Retirement Plans |  | Other Postretirement Benefit Plans
| (In thousands) |  | 2018 |  | 2017 |  | 2018 |  | 2017
| Service cost |  | $ | 2,562 |  |  | $ | 2,294 |  |  | $ | 270 |  |  | $ | 187 |
| Interest cost |  | 3,782 |  |  | 3,858 |  |  | 214 |  |  | 167 |
| Expected return on plan assets |  | (5,570 | ) |  | (5,036 | ) |  | (1,588 | ) |  | (1,312 | )
| Recognized net actuarial loss |  | 1,785 |  |  | 1,535 |  |  | (46 | ) |  | — |
| Amortization of prior service cost |  | (87 | ) |  | (107 | ) |  | (1,026 | ) |  | (1,662 | )
| Net periodic benefit cost (benefit) |  | $ | 2,472 |  |  | $ | 2,544 |  |  | $ | (2,176 | ) |  | $ | (2,620 | )

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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 -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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