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Retirement Plans and Other Post-Retirement Benefits (Tables) | 3 Months Ended
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Mar. 31, 2018
Compensation And Retirement Disclosure [Abstract] |
Schedule of Net Periodic Costs of Pension and Post Retirement Medical Benefit Plans | The following tables provide information with respect to the net periodic costs of our pension and post-retirement medical benefit plans.
|  | Three months ended March 31 |
In thousands |  | 2018 |  |  |  | 2017 |
Pension Benefits |  |  |  |  |  |  |  |  |
Service cost |  | $ | 2,859 |  |  |  | $ | 2,721 |
Interest cost |  |  | 5,589 |  |  |  |  | 5,907 |
Expected return on plan assets |  |  | (10,839 | ) |  |  |  | (10,831 | )
Amortization of prior service cost |  |  | 780 |  |  |  |  | 704 |
Amortization of unrecognized loss |  |  | 3,390 |  |  |  |  | 2,822 |
Total net periodic benefit cost |  | $ | 1,779 |  |  |  | $ | 1,323 |
Other Benefits |  |  |  |  |  |  |  |  |
Service cost |  | $ | 307 |  |  |  | $ | 295 |
Interest cost |  |  | 451 |  |  |  |  | 485 |
Amortization of prior service credit |  |  | (45 | ) |  |  |  | (45 | )
Amortization of actuarial gain |  |  | (73 | ) |  |  |  | (143 | )
Total net periodic benefit cost |  | $ | 640 |  |  |  | $ | 592 |

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- Definition Tabular disclosure of one or more of the entity's defined benefit pension plans or one or more other defined benefit postretirement plans, separately for pension plans and other postretirement benefit plans including the entity's schedule of fair value of plan assets for defined benefit or other postretirement plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2439-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2417-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2410-114920 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=77993564&loc=d3e4179-114921 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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