Pension and Other Postretirement Benefits (Components of Net Periodic Postretirement Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Ultimate healthcare trend rates	3.80%
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 10	$ 17	$ 18
Interest cost	172	234	233
Amortization of unrecognized prior service cost	44	44	44
Loss amortization (2)	64	51	132
Net periodic pension cost	$ 290	$ 346	$ 427
Discount rate	2.00%	2.90%	4.10%
Annual rate of increase in the per capita cost of: Medical costs before age 65	7.00%	6.80%	7.00%
Annual rate of increase in the per capita cost of: Medical costs after age 65	4.50%	4.50%	5.00%
Annual rate of increase in the per capita cost of: Prescription drug costs	7.00%	7.00%	9.50%