Retirement and Post-Retirement Employee Benefit Plans - Schedule of Assumptions Used (Details)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Defined Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Discount rate Pension Liability	4.38%	3.89%
Discount rate Pension Cost	3.89%	3.73%	4.55%
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	6.75%	6.75%
Expected return on plan assets Pension Cost	6.75%	7.00%	7.00%
Supplemental Executive Retirement Plans
Defined Benefit Plan Disclosure [Line Items]
Discount rate Pension Liability	4.38%	3.89%
Discount rate Pension Cost	4.08%	3.73%	4.55%
Rate of compensation increase Pension Liability	3.50%	3.50%
Rate of compensation increase Pension Cost	3.50%	3.50%	3.50%