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Employee Benefit Plans, Financial Instruments Recorded At Fair Value On A Recurring Basis By The Plan (Details) - Pension Benefits [Member] - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
--- | --- | --- | ---
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | $ 124,226 | $ 116,216 | $ 107,529
Recurring Basis [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 124,226 | 116,216 |
Recurring Basis [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 74,939 | 65,443 |
Recurring Basis [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 49,287 | 50,773 |
Recurring Basis [Member] | Cash and Cash Equivalents [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 3,684 | 3,500 |
Recurring Basis [Member] | Cash and Cash Equivalents [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 3,684 | 3,500 |
Recurring Basis [Member] | Cash and Cash Equivalents [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 0 | 0 |
Recurring Basis [Member] | Foreign Equity Mutual Funds [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 44,508 | 33,687 |
Recurring Basis [Member] | Foreign Equity Mutual Funds [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 44,508 | 33,687 |
Recurring Basis [Member] | Foreign Equity Mutual Funds [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 0 | 0 |
Recurring Basis [Member] | Equity Mutual Funds [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 26,747 | 28,256 |
Recurring Basis [Member] | Equity Mutual Funds [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 26,747 | 28,256 |
Recurring Basis [Member] | Equity Mutual Funds [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 0 | 0 |
Recurring Basis [Member] | US Government Bonds [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 99 | 1,283 |
Recurring Basis [Member] | US Government Bonds [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 0 | 0 |
Recurring Basis [Member] | US Government Bonds [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 99 | 1,283 |
Recurring Basis [Member] | Corporate Bonds [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 49,188 | 49,490 |
Recurring Basis [Member] | Corporate Bonds [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 0 | 0 |
Recurring Basis [Member] | Corporate Bonds [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | $ 49,188 | $ 49,490 |

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- Definition Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees. + 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 (b) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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