Special Charges (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost and Reserve [Line Items]
Special charge	$ 41.5	$ 28.4	$ 77.6
Gain (Loss) Related to Litigation Settlement			(1.2)
Restructuring charges	14.6	16.4
Gain (Loss) on Disposition of Business			24.5
Facility Closing [Member] | Site Consolidation [Member]
Restructuring Cost and Reserve [Line Items]
Special charge	5.8	7.3	15.9
Other Restructuring [Member] | Business Optimization [Member]
Restructuring Cost and Reserve [Line Items]
Special charge	13.1	19.8	38.4
Other Restructuring [Member] | Global Restructuring Program [Member]
Restructuring Cost and Reserve [Line Items]
Special charge	15.9	1.3
Other Restructuring [Member] | Workforce Reduction Plan [Member]
Restructuring Cost and Reserve [Line Items]
Special charge	6.7
Special Charges, Gross	35.0
Other Restructuring [Member] | Information technology [Member]
Restructuring Cost and Reserve [Line Items]
Special charge	$ 22.0	2.0
MEMS [Member]
Restructuring Cost and Reserve [Line Items]
Gain (Loss) on Disposition of Business		$ 24.5
Architectural Products Business [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 30.8