Retirement and Post-Retirement Employee Benefit Plans - Schedule of Allocation of Plan Assets (Details) - Defined Benefit Plan	Sep. 30, 2019	Sep. 30, 2018
Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation	40.60%	44.30%
International equities
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation	14.50%	15.40%
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation	18.80%	16.90%
Company stock
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation	15.40%	12.70%
Other assets
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation	10.70%	10.70%
Minimum | Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation Range	35.00%
Minimum | International equities
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation Range	10.00%
Minimum | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation Range	5.00%
Minimum | Company stock
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation Range	0.00%
Minimum | Other assets
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation Range	0.00%
Maximum | Domestic equities
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation Range	55.00%
Maximum | International equities
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation Range	20.00%
Maximum | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation Range	30.00%
Maximum | Company stock
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation Range	15.00%
Maximum | Other assets
Defined Benefit Plan Disclosure [Line Items]
Targeted Allocation Range	20.00%