Retirement Plan and Other Post-Retirement Benefits - Schedule of Health Care Cost Trend Rates (Details)	12 Months Ended
	Sep. 30, 2025		Sep. 30, 2024		Sep. 30, 2023
Retirement Benefits [Abstract]
Rate of Medical Cost Increase for Pre Age 65 Participants	7.25%	[1]	6.25%	[2]	6.25%	[3]
Rate of Medical Cost Increase for Post Age 65 Participants	5.75%	[1]	5.75%	[2]	5.00%	[3]
Annual Rate of Increase in the Per Capita Cost of Covered Prescription Drug Benefits	11.75%	[1]	10.25%	[2]	6.85%	[3]
Annual Rate of Increase in the Per Capita Medicare Part B Reimbursement	5.75%	[1]	5.75%	[2]	5.00%	[3]
Annual Rate of Increase in the Per Capita Medicare Part D Subsidy	4.00%	[1]	4.00%	[2]	6.60%	[3]
Ultimate health care trend rate	4.00%		4.00%		4.00%

[1] It was assumed that this rate would gradually decline to 4% by 2050.

[2] It was assumed that this rate would gradually decline to 4% by 2049.

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