Retirement Plan and Other Post-Retirement Benefits - Schedule of Health Care Cost Trend Rates (Details)	12 Months Ended
	Sep. 30, 2023		Sep. 30, 2022		Sep. 30, 2021
Retirement Benefits [Abstract]
Rate of Medical Cost Increase for Pre Age 65 Participants	6.25%	[1]	5.30%	[2]	5.38%	[2]
Rate of Medical Cost Increase for Post Age 65 Participants	5.00%	[1]	4.84%	[2]	4.84%	[2]
Annual Rate of Increase in the Per Capita Cost of Covered Prescription Drug Benefits	6.85%	[1]	6.29%	[2]	6.53%	[2]
Annual Rate of Increase in the Per Capita Medicare Part B Reimbursement	5.00%	[1]	4.84%	[2]	4.84%	[2]
Annual Rate of Increase in the Per Capita Medicare Part D Subsidy	6.60%	[1]	5.96%	[2]	6.15%	[2]
Ultimate health care trend rate	4.00%		4.00%		4.00%

[1] It was assumed that this rate would gradually decline to 4% by 2048.

[2] It was assumed that this rate would gradually decline to 4% by 2046.