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Employee Benefit Plans (Components of Net Periodic Benefit Expense) (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Compensation And Retirement Disclosure [Abstract]        
Service cost $ 924 $ 801 $ 2,770 $ 2,405
Interest cost on projected benefit obligation 635 696 1,905 2,086
Expected return on plan assets (1,284) (1,184) (3,852) (3,552)
Amortization of unrecognized prior service credit (8) (16) (26) (49)
Amortization of unrecognized net actuarial loss 321 366 967 1,098
Net periodic benefit expense $ 588 $ 663 $ 1,764 $ 1,988