Retirement and Postretirement Benefit Plans (Schedule of Fair Value Measurements of Plan Assets) (Details) - USD ($)	Sep. 30, 2020	Sep. 30, 2019
Pension Plan [Member] | Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets for Plan Benefits, Defined Benefit Plan	$ 2,100,000	$ 4,200,000
Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets for Plan Benefits, Defined Benefit Plan	289,600,000	306,400,000
Fair Value Measured at Net Asset Value Per Share [Member] | Fixed income securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets for Plan Benefits, Defined Benefit Plan	191,000,000.0	206,600,000
Fair Value Measured at Net Asset Value Per Share [Member] | U.S. companies [Member] | Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets for Plan Benefits, Defined Benefit Plan	49,700,000	49,600,000
Fair Value Measured at Net Asset Value Per Share [Member] | International companies [Member] | Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets for Plan Benefits, Defined Benefit Plan	$ 48,900,000	$ 50,200,000