Employee Retirement Plans - Actuarial Assumptions for Domestic Plans (Details) - Pension Benefits	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Weighted-average assumptions:
Discount rate – benefit obligations	3.13%	2.90%	3.30%
Discount rate – benefit cost	2.90%	3.30%	4.40%
Expected return on plan assets	7.10%	7.20%	7.30%
Rate of increase in salary levels	3.25%	3.25%	3.25%