Restructuring and Other Costs - Schedule of Restructuring and Other Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Restructuring And Related Activities [Abstract]
Restructuring	$ 24.3	$ 21.2	$ 50.0	$ 25.6
Other	10.5	10.5	39.2	22.4
Restructuring and other costs	$ 34.8	$ 31.7	$ 89.2	$ 48.0