Retirement Plans (Amounts Recognized for Pension and Other Postretirement Benefit Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Projected benefit obligations:
Service cost	$ 1.5	$ 1.6	$ 1.8
Interest cost	11.2	13.9	14.3
Decrease in obligation due to curtailment / settlement	0.0	(6.5)
Plan assets:
Beginning of year	351.6
Defined Benefit Plan, Plan Assets, Contributions by Employer	0.1	0.6
End of year	360.4	351.6
Recognized on balance sheet:
Pension asset	0.9	0.0
Other noncurrent liabilities	0.0	(5.0)
Recognized in accumulated other comprehensive loss, before tax:
Other	0.0	(0.2)
Pension Plan, Defined Benefit [Member]
Projected benefit obligations:
Beginning of year	356.6	333.4
Service cost	1.5	1.6
Interest cost	11.2	13.9
Actuarial loss (gain)	13.7	38.2
Benefits paid	(23.5)	(23.9)
Currency translation	0.0	(0.1)
Decrease in obligation due to curtailment / settlement	0.0	6.5
End of year	359.5	356.6	333.4
Accumulated benefit obligation at end of year	359.5	356.6
Plan assets:
Beginning of year	351.6	343.5
Actual return on plan assets	32.2	38.6
Currency translation	0.0	(0.5)
Benefits paid	(23.5)	(23.9)
End of year	360.4	351.6	$ 343.5
Accrued benefit cost at end of year:
Unfunded status	0.9	(5.0)
Recognized on balance sheet:
Pension asset	0.9	0.0
Other noncurrent liabilities	0.0	(5.0)
Amount recognized on balance sheet	0.9	(5.0)
Recognized in accumulated other comprehensive loss, before tax:
Net actuarial loss (gain)	74.0	78.4
Recognized in accumulated other comprehensive loss, before tax	$ 74.0	$ 78.4