Pension and Other Retirement Plans (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) employee	Dec. 31, 2019 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Actuarial gains (losses)	$ (1,050)	$ 5,100
401(K) Plan [Member]
Defined Contribution Plans
Maximum pretax contribution per employee	100.00%
Defined contribution plan, employer matching contribution, percent	1.50%
Expense recognized	$ 741	702
Other Post-Employment Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic cost (benefit)	19	9
Recorded liabilities	1,372	1,347
Actuarial gains (losses)	$ (42)	$ (182)
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate of projected benefit obligation	2.10%	2.90%
Discount rate, net periodic pension expense (benefit)	2.90%	4.00%
Expected long-term return on plan assets	6.50%	6.50%
Net periodic cost (benefit)	$ (4,646)	$ (3,290)
Actuarial gains (losses)	$ (1,008)	$ 5,282
Defined Contribution Plans
Number of employee participants | employee	1,400
Pension Plan [Member] | Equity Securities [Member]
Defined Benefit Plan, Assets, Target Allocations
Target allocation of plans' assets	45.00%
Allocation of plans' assets	43.90%
Pension Plan [Member] | Fixed Income Securities [Member]
Defined Benefit Plan, Assets, Target Allocations
Target allocation of plans' assets	55.00%
Allocation of plans' assets	56.10%