Retirement and Postretirement Employee Benefit Plans - Schedule of Assumptions Used (Details)	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Employee Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate pension liability	5.66%	2.97%
Discount rate pension cost	2.97%	2.80%	3.29%
Rate of compensation increase pension liability	3.50%	3.50%
Rate of compensation increase pension cost	3.50%	3.50%	3.50%
Expected return on plan assets pension liability	6.25%	6.25%
Expected return on plan assets pension cost	6.25%	6.25%	6.50%
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
Defined Benefit Plan Disclosure [Line Items]
Discount rate pension liability	5.71%	2.57%
Discount rate pension cost	2.57%	2.90%	3.19%
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%