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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