Employee Benefits And Deferred Compensation Plans (Schedule Of Assumptions Used, SERP) (Details) - Supplemental Executive Retirement Plan [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Discount rate for projected benefit obligation	3.09%	3.30%	3.38%
Discounted rate for net periodic pension cost	3.30%	3.38%	3.30%
Salary scale	3.00%	3.00%	3.50%