Retirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Service cost	$ 1.5	$ 1.6	$ 1.8
Interest cost	11.2	13.9	14.3
Expected return on plan assets	(16.9)	(16.2)	(16.5)
Amortization of net loss (gain)	2.8	1.9	3.2
Curtailment / special settlement loss (gain)	0.0	0.7	0.0
Other	(0.1)	0.1	0.0
Defined Benefit Plan, Net Periodic Benefit Cost other than Service Cost	(3.0)	0.4	1.0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	(1.5)	2.0	$ 2.8
Pension Plan, Defined Benefit [Member]
Service cost	1.5	1.6
Interest cost	$ 11.2	13.9
Curtailment / special settlement loss (gain)		$ (1.1)