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Employee Benefit Plans (Schedule of SERP's Pension Cost) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost - benefits earned during the year | $ 3,554 | $ 4,017 |
Interest cost on projected benefit obligations | 4,103 | 3,703 |
Supplemental Executive Retirement Plan [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Service cost - benefits earned during the year | 97 | 92 | $ 143
Interest cost on projected benefit obligations | 408 | 348 | 360
Net amortization and deferral | 276 | 581 | 324
Net periodic pension cost | $ 781 | $ 1,021 | $ 827

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