Employee Benefit Plans (Schedule Of Assumptions Used To Develop Periodic Expense) (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Discount rate	3.09%	4.12%	3.50%
Salary scale increases	3.50%	3.50%	3.50%
Long-term rate of return on assets	7.00%	7.00%	7.00%
Interest credit rate for cash balance plan	4.50%	4.50%	4.50%