Restructuring (Restructuring Reserve by Type of Cost) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
2019 Integration Related Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance		$ 8.2	$ 9.8
Restructuring Charges		20.0	29.1	$ 12.1
Utilized, Cash		15.7	18.7
Utilized, Non-Cash		8.4	12.0
Restructuring Reserve, Ending Balance	$ 4.1	4.1	8.2	9.8
2020 Cost Structure Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance		1.2	0.0
Restructuring Charges		16.8	1.2	0.0
Utilized, Cash		16.4	0.0
Utilized, Non-Cash		0.0	0.0
Restructuring Reserve, Ending Balance	1.6	1.6	1.2	0.0
Severance & termination related costs | 2019 Integration Related Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance		5.3	9.8
Restructuring Charges		0.1	0.8
Utilized, Cash		4.0	5.3
Utilized, Non-Cash		0.0	0.0
Restructuring Reserve, Ending Balance	1.4	1.4	5.3	9.8
Severance & termination related costs | 2020 Cost Structure Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance		0.4	0.0
Restructuring Charges		1.2	0.4
Utilized, Cash		0.7	0.0
Utilized, Non-Cash		0.0	0.0
Restructuring Reserve, Ending Balance	0.9	0.9	0.4	0.0
Accelerated depreciation & asset write-offs | 2019 Integration Related Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance		0.0	0.0
Restructuring Charges		6.7	12.0
Utilized, Cash		0.0	0.0
Utilized, Non-Cash		6.7	12.0
Restructuring Reserve, Ending Balance	0.0	0.0	0.0	0.0
Gain on sale of fixed assets | 2019 Integration Related Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance		0.0
Restructuring Charges		(3.3)
Utilized, Cash	5.5
Utilized, Non-Cash		1.7
Restructuring Reserve, Ending Balance	0.5	0.5	0.0
Other exit costs | 2019 Integration Related Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance		2.9	0.0
Restructuring Charges		16.5	16.3
Utilized, Cash		17.2	13.4
Utilized, Non-Cash		0.0	0.0
Restructuring Reserve, Ending Balance	2.2	2.2	2.9	0.0
Other exit costs | 2020 Cost Structure Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve, Beginning Balance		0.8	0.0
Restructuring Charges		15.6	0.8
Utilized, Cash		15.7	0.0
Utilized, Non-Cash		0.0	0.0
Restructuring Reserve, Ending Balance	$ 0.7	$ 0.7	$ 0.8	$ 0.0