Restructuring and Other Costs - Schedule of Changes in Restructuring Accrual Charges (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Restructuring And Other Costs [Abstract]
Accrual at beginning of fiscal year	$ 31.6	$ 47.4
Additional accruals	37.5	11.2
Payments	(32.9)	(24.3)
Adjustment to accruals	(3.1)	0.3
Foreign currency rate changes	0.1	(1.3)
Accrual at June 30	$ 33.2	$ 33.3