Retirement Plan And Other Post-Retirement Benefits (Schedule Of Health Care Cost Trend Rates) (Details)		12 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Retirement Benefits [Abstract]
Rate of Medical Cost Increase for Pre Age 65 Participants	[1]	5.42%	5.50%	5.59%
Rate of Medical Cost Increase for Post Age 65 Participants	[1]	4.75%	4.75%	4.75%
Annual Rate of Increase in the Per Capita Cost of Covered Prescription Drug Benefits	[1]	6.80%	7.35%	7.89%
Annual Rate of Increase in the Per Capita Medicare Part B Reimbursement	[1]	4.75%	4.75%	4.75%
Annual Rate of Increase in the Per Capita Medicare Part D Subsidy	[1]	6.20%	6.84%	7.18%
Ultimate Health Care Trend Rate		4.50%	4.50%	4.50%

[1] It was assumed that this rate would gradually decline to 4.5% by 2039.