Retirement and Postretirement Benefit Plans (Schedule of Postretirement Health Care Plan) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Change in benefit obligation:
Benefit obligation at beginning of year	$ 334.6
Benefit obligation at end of year	380.4	$ 334.6
Amounts recorded in the Consolidated Balance Sheets:
Accrued benefits obligation, long-term	80.8	69.3
Postretirement Health Coverage [Member]
Change in benefit obligation:
Benefit obligation at beginning of year	17.0	19.4
Service cost	0.3	0.3
Interest cost	0.5	0.6
Actuarial gain	(4.1)	(2.4)
Defined Benefit Plan, Benefit Obligation, Benefits Paid	1.3	1.2
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant	0.3	0.3
Benefit obligation at end of year	12.7	17.0
Amounts recorded in the Consolidated Balance Sheets:
Accrued benefits obligation, current portion	1.3	1.6
Accrued benefits obligation, long-term	11.4	15.4
Net amount recognized	$ 12.7	$ 17.0