Restructuring and Other Costs - Schedule of Changes in Restructuring Accrual Charges (Details) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Restructuring And Other Costs [Abstract]
Accrual at beginning of fiscal year	$ 32.3	$ 31.6
Additional accruals	27.5	32.3
Payments	(27.3)	(24.2)
Adjustment to accruals	(1.9)	(2.7)
Foreign currency rate changes		(0.1)
Accrual at March 31	$ 30.6	$ 36.9