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Employee Benefit Plans Employee Benefit Plans 11 (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Healthcare Cost Trend Rate |  |  |  |
Initial health care cost for employees under age of 65 (as a percent) | 6.20% |  |  |
Ultimate health care cost for employees under age of 65 (as a percent) | 4.50% |  |  |
Initial Health care cost for employees of age 65 and over (as a percent) | 6.20% |  |  |
Ultimate health care cost for employees of age 65 and over (as a percent) | 4.40% |  |  |
Effects of one-percentage-point change in assumed health care cost trend rates |  |  |  |
Effect on total of service and interest cost components -1 Percentage Point Increase | $ 45 |  |  |
Effect on total of service and interest cost components -1 Percentage Point Decrease | (39) |  |  |
Effect on post-retirement benefit obligation -1 Percentage Point Increase | 894 |  |  |
Effect on post-retirement benefit obligation -1 Percentage Point Decrease | $ (769) |  |  |
Union plan |  |  |  |
Employee benefit plans |  |  |  |
Expected long-term return on plan assets | 6.00% | [1] | 7.00% | 7.00%
Non-union plan |  |  |  |
Employee benefit plans |  |  |  |
Expected long-term return on plan assets | 4.20% | [1] | 4.20% | 4.20%
[1] | *6.0% for union plan and 4.2% for non-union (net of income taxes) in 2017, and 7.00% for union plan and 4.20% for non-union (net of income taxes) for 2016 and 2015.

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- Definition Represents the initial health care cost for employees of age sixty-five and over. + References No definition available. + Details
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- Definition Represents the initial health care cost for employees under age of sixty-five. + References No definition available. + Details
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- Definition The ultimate trend rate for health care costs for employees of age sixty-five and over. + References No definition available. + Details
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- Definition The ultimate trend rate for health care costs for employees under age of sixty-five. + References No definition available. + Details
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- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan. + 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 (k)(3) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate. + 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 (m) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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