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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, 2020 | Dec. 31, 2019 | Dec. 31, 2018
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Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | $ 128,563 | $ 122,995 | $ 109,746
Recurring Basis [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 128,563 | 122,995 |
Recurring Basis [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 80,098 | 74,268 |
Recurring Basis [Member] | Level 2 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 48,465 | 48,727 |
Recurring Basis [Member] | Cash and Cash Equivalents [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 3,461 | 4,143 |
Recurring Basis [Member] | Cash and Cash Equivalents [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 3,461 | 4,143 |
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 | 41,000 | 40,239 |
Recurring Basis [Member] | Foreign Equity Mutual Funds [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 41,000 | 40,239 |
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 | 35,637 | 29,886 |
Recurring Basis [Member] | Equity Mutual Funds [Member] | Level 1 [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 35,637 | 29,886 |
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 | 47 | 58 |
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 | 47 | 58 |
Recurring Basis [Member] | Corporate Bonds [Member] |  |  |
Defined Benefit Plan, Information about Plan Assets [Abstract] |  |  |
Fair value of plan assets | 48,418 | 48,669 |
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 | $ 48,418 | $ 48,669 |

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