Employee Benefit Plans (Benefit Obligations in Excess of the Fair Value of Plan's Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Employee Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 107,824	$ 102,607	$ 95,869
Accumulated benefit obligation	107,824	102,607
Fair value of plans' assets	71,940	73,357	$ 63,109
Projected benefit obligation greater than fair value of plans' assets	35,884	29,250
Accumulated benefit obligation greater than fair value of plans' assets	35,884	29,250
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	104,657	99,515
Accumulated benefit obligation	104,657	99,515
Fair value of plans' assets	71,940	73,357
Projected benefit obligation greater than fair value of plans' assets	32,717	26,158
Accumulated benefit obligation greater than fair value of plans' assets	32,717	26,158
Benefit Equalization Plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	3,167	3,092
Accumulated benefit obligation	3,167	3,092
Fair value of plans' assets	0	0
Projected benefit obligation greater than fair value of plans' assets	3,167	3,092
Accumulated benefit obligation greater than fair value of plans' assets	$ 3,167	$ 3,092