Retirement and Postretirement Employee Benefit Plans - Asset Allocation (Details)	Sep. 30, 2022	Sep. 30, 2021
Employee Pension Plan | Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Asset allocation	39.70%	44.50%
Employee Pension Plan | Domestic equities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation  Range	35.00%
Employee Pension Plan | Domestic equities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation  Range	55.00%
Employee Pension Plan | International equities
Defined Benefit Plan Disclosure [Line Items]
Asset allocation	14.60%	16.90%
Employee Pension Plan | International equities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation  Range	10.00%
Employee Pension Plan | International equities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation  Range	20.00%
Employee Pension Plan | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Asset allocation	16.00%	16.00%
Employee Pension Plan | Fixed income | Minimum
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation  Range	5.00%
Employee Pension Plan | Fixed income | Maximum
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation  Range	30.00%
Employee Pension Plan | Company stock
Defined Benefit Plan Disclosure [Line Items]
Asset allocation	15.30%	10.60%
Employee Pension Plan | Company stock | Minimum
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation  Range	0.00%
Employee Pension Plan | Company stock | Maximum
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation  Range	15.00%
Employee Pension Plan | Other assets
Defined Benefit Plan Disclosure [Line Items]
Asset allocation	14.40%	12.00%
Employee Pension Plan | Other assets | Minimum
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation  Range	0.00%
Employee Pension Plan | Other assets | Maximum
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation  Range	20.00%
Postretirement Plan | Diversified investment funds
Defined Benefit Plan Disclosure [Line Items]
Asset allocation	97.70%	97.90%
Postretirement Plan | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Asset allocation	2.30%	2.10%