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Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2019 | Mar. 31, 2018 | Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year |  |  | $ 1,800
Post-Retirement Health Benefits [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Defined Benefits Plan Estimated Future Employer Contributions In Next Fiscal Year |  |  | $ 233
Service cost | $ 9 | $ 10 |
Interest cost | 36 | 33 |
Expected return on plan assets | 0 | 0 |
Defined Benefit Plan, Amortization of Prior Service Cost (Credit) | 0 | 0 |
Net amortization of net (gain) loss | (4) | 0 |
Net Periodic Benefit Cost | 41 | 43 |
Defined Benefit Plan, Plan Assets, Contributions by Employer | 56 |  |
Pension Plan [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost | 304 | 347 |
Interest cost | 866 | 798 |
Expected return on plan assets | (896) | (991) |
Defined Benefit Plan, Amortization of Prior Service Cost (Credit) | 0 | 0 |
Net amortization of net (gain) loss | 389 | 362 |
Net Periodic Benefit Cost | 663 | $ 516 |
Defined Benefit Plan, Plan Assets, Contributions by Employer | $ 391 |  |

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- Definition Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(5) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(5) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920 + Details
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- Definition Amount of contribution received by defined benefit plan from employer which increases plan assets. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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