Retirement and Postretirement Employee Benefit Plans - Schedule of Assumptions Used (Details)	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Oct. 01, 2026	Sep. 30, 2026
Employee Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate pension asset	5.45%	5.02%
Discount rate pension cost	5.02%	6.10%	5.66%
Rate of compensation increase pension asset	3.50%	3.50%
Rate of compensation increase pension cost	3.50%	3.50%	3.50%
Expected return on plan assets pension asset	6.50%	6.50%
Expected return on plan assets pension cost	6.50%	6.25%	6.25%
Interest crediting rate increase pension asset	4.69%	4.69%
Interest crediting rate increase pension cost	4.69%	4.69%	4.69%
Employee Pension Plan | Forecast
Defined Benefit Plan Disclosure [Line Items]
Interest crediting rate increase pension asset				4.69%	4.73%
Supplemental Executive Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate pension liability	5.14%	4.92%
Discount rate pension cost	4.92%	5.85%	5.50%
Rate of compensation increase pension liability	3.50%	3.50%
Rate of compensation increase pension cost	3.50%	3.50%	3.50%
Interest crediting rate increase pension liability	4.69%	4.69%
Interest crediting rate increase pension cost	4.69%	4.69%	4.69%
Supplemental Executive Retirement Plans | Forecast
Defined Benefit Plan Disclosure [Line Items]
Interest crediting rate increase pension liability				4.69%	4.73%